Ambiphilic coal body surfaces

ABSTRACT

The invention provides compositions of matter comprising coal body surfaces having improved characteristics for hydration and preservation of pristine surfaces, and which are compatible with both hydrophilic and hydrophobic liquid media. The coal body surfaces of the invention facilitate burning at low temperatures, avoiding emissions of nitrogen oxides, and also have improved properties for surfactant-free suspension in either water or oil media, as well as for liquefaction and gasification.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/065,614, filed Feb. 13, 2008, and a U.S. Provisional PatentApplication filed Feb. 9, 2009 for which an application no. has not yetbeen assigned at the time of this filing, each entitled “Apparatus andProcesses for Improved Utilization of Fuel Solids,” and incorporates byreference the contents of both applications in their entirety.

FIELD OF THE INVENTION

This application pertains to compositions of matter comprising a coalwith improved surface characteristics.

BACKGROUND OF THE INVENTION

Approximately 50% of the energy demand in the United States is currentlysatisfied by the combustion of coal, and the total energy value ofremaining U.S. coal deposits exceeds the energy content of naturalreserves for all other types of fuels combined. Retrofitting thenational coal infrastructure to use other types of fuels is expected torequire many years and enormous investments of new working capital.Indeed, a complete conversion to non-coal energy sources in the nearfuture would drive energy prices to levels that most consumers are notprepared to pay. Thus although the environmental impact of coal use is asource of ongoing controversy, coal will nevertheless remain animportant energy resource for the foreseeable future.

The problems with coal use arise partly from its composition andlocation. Coal, like peat, is a complex biomass material resulting fromanaerobic bacterial degradation of accumulated dead plant matter underpressure. Coal is largely carbonaceous, but because of its botanicalsource coal often contains heteroatoms such as sulfur and nitrogen thatundergo chemical processes to form pollutants when burned. The greatestcoal reserves are, in fact, the low-ranked varieties having substantialamounts of sulfur and nitrogen. Furthermore the burning of coal convertsambient atmospheric dinitrogen to gaseous brown nitrogen oxides, whichare pollutants and characteristic components of smog. And coalcombustion also generates large quantities of carbon dioxide, agreenhouse gas that has a role in climate change. Underground coal actsas a type of filter for toxic elements in groundwater, thus coal alsocontains significant amounts of arsenic, chromium, mercury andradioactive species such as radium.

Direct combustion of coal can also be quite inefficient. This is partlybecause coal is a very wet material. By weight, coal as mined oftencontains 30% water or more. When coal is burned in that condition thewater is baked off as water vapor in an unrecoverable energy loss unlesssteps are taken to dry the coal before burning or to harness the energyof the emitted water vapor. Yet even for dry coal the combustion rate isoften lower and less uniform than desired.

Coal is also inefficient as a candidate for transport. Traditionallycoal has been shipped in lump form by barge or railroad car for longdistances. In modern times slurries have been made consisting ofapproximately 30% finely ground coal by weight in water or light oil;such compositions are suitable for transport by pipeline, andconveniently they are also suitable for burning and can be substitutesfor diesel fuel. However slurry generation for a pipeline requires anample supply of water or oil at the pipeline's outermost point. Andconventional coals have many deleterious effects, including eroding andagglomeration, as well as plugging pumps, valves and boiler tubes Formany major coal deposits such as those found in the Midwest, thatprerequisite often cannot be satisfied.

Conversion of coal to other fuel sources is also energy-intensive. Itsgasification requires temperatures above about 1100° F. at atmosphericpressure: most gasifiers currently operate at 2600-2800° F. becauselower temperatures produce large quantities of tars, phenols and coke.Direct liquefaction of coal is typically conducted in the range of650-750° F. and 20 bars of pressure. Catalysts are often used at up to 2weight percent relative to coal to aid these processes, however suchcatalysts are not distributed very finely or uniformly in coal mixturesand thus the catalysis efficiencies are hardly optimal.

Traditional milling of coal also entails high maintenance expense,unpredictable downtime and wide, variable particle size distributionbecause mechanical crushing or grinding causes considerable wear onexposed parts of the mill

There is therefore a need for improved coal types, improved combustionprocesses and related equipment that will result in relatively lesspollution, higher efficiency in converting coal to usable energy, higherefficiency in conversion to other fuels, and higher efficiency inmilling.

SUMMARY OF THE INVENTION

The invention provides an improved fuel processing device, wherein solidfuels are comminuted by entrainment within a shear field of superheatedsteam within a reaction chamber, classified in vortexes of steamtherein, and then dehydrated to a partial but optimal extent by ahydration modulating unit. Optionally the device may be used to addcatalysts; absorbents; reducing agents; and gases such as natural gas,dihydrogen, carbon monoxide, carbon dioxide, syngas, or hydrogen sulfideto the fuel. Inner surfaces of a reaction chamber in the device may beprotected by a thermal blanket, insert, tiles, or other protection suchthat the chamber may be employed under reaction conditions in the rangeof those required for liquefaction or gasification of fuels. Optionallythe device may be in line with a scrubber, gasifier unit, or liquefierunit. Optionally the device may have an apparatus for introduction offuel particles. And optionally the hydration of the fuel product may bemodulated by a governor for metering steam or a cooling mist, or mayemploy a re-wetting of dried fuel.

Advantages of the comminuted particles include shorter reaction times tocomplete liquefaction, gasification, combustion and cracking. Theparticles can also burn at lower temperatures than conventional fuels,burning lower than even conventionally micronized coals and avoidinggeneration of nitrogen oxide pollutants without compromising energyyields. The uniformity and porosity of the particles of the inventionallow them to be processed with more uniform temperatures, fasterheating in the particle interiors, and faster mass transfer at virgincoal surfaces. The comminuted particles also have ambiphilic propertiesenabling surfactant-free suspensions, and have reduced-wearcharacteristics on mechanical parts.

The invention further provides an improved process for modifying fuelparticles, wherein fuel solids up to 3 inches in diameter are comminutedin the shear field at 650° F. or more with an initial steam velocity of1340 ft/s or more, and are then dehydrated to about 0.5 to 5.0% or morewater by weight relative to the fuel solids. The process may optionallycoat the external and internal surfaces of the resulting particles withone or more substance that catalyze or are catalyst precursors forcombustion, gasification, methanation, or liquefaction. The inventionalso provides a process for making improved suspensions of fuel solidsin liquid media by adding the comminuted dried particles to liquid mediadirectly, or by scrubbing superheated steam in liquid media in which thefuel particles are entrained. The fuels may be coal, biomass, syntheticpolymers, petroleum coke, and or other fuel solids.

The invention also provides an improved type of ground coal having anadvantageous hydration layer, and having the same or better low density,surface area and porosity than the native, unground coal, instead ofbeing compromised as in conventionally ground coal. The improved type ofground coal can burn essentially completely at a lower temperature thanconventional coal, thereby avoiding formation of nitrogen oxidecompounds from ambient atmospheric nitrogen, and can also behydrocracked essentially completely at a lower temperature thanconventional coal. The coal of the invention forms stable suspensionswithout surfactants in both hydrophobic and hydrophilic liquid media;these suspensions may be burned, gasified or liquefied readily. Theimproved coal may optionally contain catalysts at its interior and orexterior particle surfaces. The invention also provides an improvedlow-pollution fuel for combustion.

Moreover, the invention provides an improved coal body surface orresinous wood body surface in which the surface is ambiphilic, and alsohas a beneficial hydration layer. The hydration layer preventsaggregation between coal particles, thereby making them more susceptibleto heat transfer to the inner cores of the particles and thus betterable to burn at low temperatures, and the hydration layer also reducescoal aggregation. The porosity and ability to use uniform applicationtemperatures facilitates devolatilization and avoids conversion to tarsand other unwanted byproducts. The hydration layer is believed to bestable up to 300° C. (ca. 570° F.) at ambient pressure. Optionally thehydration layer may also contain a catalyst, absorbent,hydrogen-donating organic substance or other substance dissolved in orotherwise disposed in or at the hydration layer.

The invention provides an improved process for combustion wherein fuelparticles made according to the improved modification process above burnat a temperature low enough to avoid creating nitrogen oxide thermalbyproducts from deleterious oxidation of atmospheric nitrogen. Theparticles may optionally also contain combustion catalysts.

The invention also provides for injection of liquefying gases such ashydrogen, carbon monoxide, carbon dioxide and or low alkanes into thegrinder to facilitate rapid liquefaction. The invention further providesan improved process for liquefaction wherein fuel particles madeaccording to the improved modification process above contain catalystsfor hydrogenation and or cracking, and wherein the cracking catalystsare relatively inert until the cracking phase of a thermal step functiontreatment. The improved process has accelerated liquefaction rates forliquid medium suspensions under standard liquefaction conditions. I.e.,carbon monoxide and hydrogen pressure are used in the dissolutiontemperature range of ambient to 650° F. The process reduces thedissolution product with dihydrogen and or a hydrogen donor solvent,using a catalyst such as molybdenum sulfide or iron sulfide in thetemperature range 650-750° F. with reaction times of an hour or less.Optionally, the process cracks the remaining fuel in the temperaturerange 750-950° F. in the presence of hydrogen and the substantialabsence of carbon monoxide, though carbon dioxide may optionally bepresent, using a cracking catalyst such as aluminum oxide. Because theprocess employs starting fuel solids in which refractory bonds aresubstantially absent and avoids introducing them, the cracking step maybe avoided entirely as desired.

The invention also provides an improved device and corresponding processfor gasification wherein fuel particles made according to the improvedmodification process above can be gasified in the substantial absence ofoxygen. That is, the process is driven by efficient allothermalprocesses involving externally applied heat as opposed to autothermalprocesses involving the partial burning of coal at the outset. Theinvention further provides slurries based on fuel microparticles,wherein the slurries produce very little wear on mechanical parts athigh flow velocities. The invention moreover provides uniformdispersions of catalysts in fuels as provided to the gasifier unit,resulting in rapid, uniform and fuel efficient gasification.Furthermore, the fuel solids as provided are non-agglomerating. And heatrecuperation from the process is sufficient to generate steam forgrinding.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 provides an illustrative embodiment of a calculation for thedehydration of comminuted coal using a steam source 650° F. (ca. 340°C.) and 200 psi by the invention apparatus and method of using it.

FIG. 2 provides an illustrative embodiment of a calculation for thedehydration of comminuted coal using a steam source 700° F. (ca. 370°C.) and 200 psi by the invention apparatus and method of using it.

FIG. 3 provides an illustrative embodiment of a calculation for thedehydration of comminuted coal using a steam source 750° F. (ca. 400°C.) and 200 psi by the invention apparatus and method of using it.

FIG. 4 provides an illustrative embodiment of products and processes bythe invention apparatus and method of using it an in-line configurationfor grinding, loading particles with catalyst, and further processing offuels.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly it has been discovered that creation of a hydration layeron the surfaces of solid fuels under certain conditions alters theirsurface properties in a stable and beneficial way. These hydrationlayers enable them to be more efficiently and selectively reacted duringcombustion, liquefaction and gasification, and to be stored insuspensions more stably. The fines are pyrophoric when dry, thus theimproved properties for handling in suspensions offer importantadvantages. Also, the hydration layers are relatively robust, and arebelieved to be stably adsorbed to carbonaceous fuel surfaces up totemperatures of approximately 570° F. (300° C.). Apparatus and methodsfor creating and using these surface-hydrated fuels are described below.In addition, the loading of particles with catalyst in the grinderprovides improved distribution and adhesion of catalyst to particles.And particles manufactured by the invention method can also be burnedefficiently with good energy yield at low temperatures and greatlyreduced pollution. Definitions of the terms as used herein are providedbelow.

Definitions

The term “housing” as used herein refers to a physical casing for anapparatus or a part thereof. Where a reaction chamber is containedwithin the housing, the housing may be distinct from or alternately ofone piece with the walls of the reaction chamber.

The term “reaction chamber” as used herein refers to a compartmentwithin which a fuel is comminuted, chemically coated or chemicallyreacted. The term “internal surface” with respect to the chamber refersto the inside surfaces of the walls of the chamber. The term “insulatingmantle” refers to a thermal liner which is optionally used to insulatethe internal surfaces of the chamber. The terms “insulating blanket,”“insulating tile,” and “insulating insert” likewise refer to thermalliners optionally used to insulate the internal surfaces of the chamber.

The terms “apparatus for introducing” and “apparatus for introduction”as used herein refers to an apparatus by which a substance may beintroduced continuously, intermittently or alternatively occasionallyinto a reaction chamber.

The term “superheated steam” as used herein refers to steam that isprovided at a temperature exceeding the boiling point of water atambient pressure. The term “superheat” as herein represents the excessof heat above the boiling point of water, which is 212° F.; thusinstance steam at 250° F. represents only 38° F. of superheat.

The term “dry steam” as used herein refers to steam that is provided ata temperature and pressure above the corresponding critical levels forcondensation.

The term “milling medium” as used herein refers to a gas such as steam,carbon dioxide, carbon monoxide, hydrogen, dinitrogen or other gas orcombination of gases in which fuel particles are entrained for thepurpose of comminution.

The term “decompression ratio” as used herein when used with regard tothe flow of steam or another gas refers to the change in pressurebetween the source and output during flow. As an example, steam that ismaintained at a pressure of 1.5 atmospheres at the source and 1.0atmospheres in the output region has a decompression ration of 1.5:1.

The term “shear field” as used herein refers to the boundary betweenslow-moving and fast-moving aerodynamic zones in the grinding chamber.

The term “vortex” as used herein refers to a distribution of steam orother gas flowing in a cyclical manner within a housing; vortexes areshed by the shear field. In a particular embodiment a shear field andvortexes of steam are provided by means of nozzles distributed atregular intervals around a circle located on a horizontal plane; thenozzles are each directed 12.5° above the plane of the horizontal, andat 12.5° all clockwise—or all counterclockwise—relative to the radiusfrom the center of the circle. In such an embodiment the shear field andvortexes are formed when a cone of steam from each nozzle intercepts therecirculation stream at the perimeter of the reaction vessel's interior,which is relatively quiescent.

The term “revolution” as used herein with respect to a shear field orvortex refers to one complete turn around the shear field or vortex.

The term “central axis” as used herein with respect to a shear field orvortex refers to the axis about which steam in the shear field or vortexrevolves.

The term “trajectory path” as used herein with respect to a shear fieldor vortex refers to the trajectory of steam and or entrained solids inthe steam at a respective point in the shear field or vortex.

The term “nozzle” as used herein refers to an apparatus through whichsteam flows from a pressurized source into a reaction chamber.

The term “entrain” as used herein with regard to a solid in steam refersto the transport of the solid in or by the steam. For a steam shearfield or steam vortex in a reaction chamber the solid may be entrainedin the steam either before entering the chamber or after beingintroduced to the reaction chamber; optionally the solid may be added toa steam shear field or vortex that has already been formed. A “means forentraining” a solid in steam may for instance be a pipe providing steamunder pressure to drive the solid into a reaction chamber.

The term “mass:heat ratio” as used herein refers to the relationshipbetween the mass and the absolute amount of heat contained in one ormore fuel solids. In particular the term is used herein to refer to themass:heat ratio present at the end of comminution, and the amount ofsuperheat required to evaporate most or all of the water contained in acomminuted fuel solid.

The term “in-line” as used herein with respect to apparatuses andprocesses refers to a relationship between apparatus units in whichmaterial is transferred through one or more direct sequential steps fromone process to another. Thus a grinding apparatus is in-line with aliquefaction unit whether the vented steam product is routed directlyinto the liquefaction unit, or is treated first in scrubber and slurryunits and then routed directly to a liquefaction unit. As contemplatedherein the term “in-line” includes automated inventorying and release ofintermediate products, such as where a slurry is sent to a holding tankuntil a liquefaction unit is ready to accept the product for chemicalconversion.

The term “hydration-modulating unit” as used herein refers to anapparatus for altering the moisture content of fuel solids that arestatic or entrained in steam or another gas, in order to provide afinite low amount of moisture on the surface of solids followingevaporation of any steam present.

The term “governor” as used herein refers to a device for imposing aceiling level on heat transfer to or from steam.

The term “cool water spraying unit” as used herein refers to a sprayingunit that provides water at a temperature below the ambient boilingpoint of steam.

The term “apparatus for re-wetting” refers to an apparatus for providingup to 5% water by weight of dehydrated or anhydrous fuel. Non-limitingexamples of such apparati include: “misting units” that provide spraysof liquid water, “steaming units” that provide steam exposures, and“sub-saturation humidifying units” that provide a humid gaseous medium.

The term “dehydrated” refers to a substance from which most or all ofthe water has been removed.

The term “semi-dehydrated” refers to a substance from which less thanall of the water has been removed.

The term “anhydrous” as used herein refers to the substantial absence ofwater.

The term “bone dry” as used herein is synonymous with the term“anhydrous”.

The term “spray dry” as used herein refers to spraying a suspension ofsolids in a liquid medium, wherein some or all of the liquid isevaporated during spraying.

The term “fuel” as used herein when used with respect to solid fuelsrefers to coal, biomass, and other carbonaceous fuels. The term “fuel”as used herein refers to materials that may be combusted directly orwhose modified materials may be combusted; alternatively the term “fuel”refers to materials whose energy may be captured by a non-combustionreaction such as in a fuel cell. The term fuel as used herein includessubstances that may be used as a fuel but which are used as a non-fuelfeedstock, e.g., as a chemical feedstock. It is contemplated that insome applications fuels may be converted to another fuel form;nonexclusive examples include the conversion of coal to a combustiblegas, and conversion of biomass first to sugars by hydrolysis and then toethanol by fermentation.

The term “coal” as used herein refers to anthracite, bituminous,subbituminous, and lignite coals, and peat.

The term “petroleum coke” as used herein refers to a carbonaceous solidderived from oil refinery coker units or other petroleum crackingprocesses.

The term “biomass” as used herein refers to matter which originates froma biological source and which may be used as a fuel source. As usedherein, the term biomass includes sawdust, wood, pulp, bark, paper,straw, lignin, chaff, bagasse, agricultural waste, forest waste, yardwaste, mulch, microbial biomass, fishery waste, feathers, fur, hoofs,manure, and other biomass such as is familiar to the person of ordinaryskill in the biomass art.

The term “run of the mine” as used herein with respect to coal refers tocoal just as it comes from the mine, containing both large and smallpieces, and with all qualities together as obtained from the mine.

The term “nugget” as used herein refers to a piece of fuel having arock-like shape and being less than about 4 inches in diameter. The termnugget as used herein also encompasses particle classifications known byother names in the art, including coal particles denominatedrespectively as rice, buckwheat, pea, nut, stove, egg, broken, stokercoal, slack, and comparable terms.

The term “comminution” as used herein refers to the act of breakingsolids into smaller pieces, without regard to the method used or thecharacteristics of the products other than size.

The term “feed coal” as used herein refers to nuggets of coal fed intothe processor of the invention.

The term “grinding aid” as used herein refers to a hard particulatematerial used to enhance abrasion and comminution in the process or theinvention. Exemplary grinding aids include sand, silica, alumina,metallic or carborundum grit; the term may also refer to the inclusionof small coal solids for aiding the grinding of soft fuels such asbiomass or synthetic polymers.

The term “grit” as used herein refers to hard inorganic or carbonaceousparticles for use in grinding.

The term “particle” as used herein refers to a small solid, which may ormay not be a product of comminution. The term as used herein is notlimiting with regard to size ranges.

The term “microparticle” as used herein refers to particles that are inthe range of 40 microns or less in average diameter.

The term “secondary substance” as used herein refers to a composition ofmatter other than the fuel solids, wherein the secondary substance issimultaneously present with the fuel solids in the reaction chamber.Illustrative examples of secondary substances include grinding aids,catalysts, catalyst precursors, absorbents, and reducing agents, amongother substances. Exemplary secondary substances include gases, such asnatural gas, hydrogen gas, carbon monoxide, carbon dioxide, syngas,methane, and other gases and gaseous mixtures. When desired, steam maybe introduced as a secondary substance, for instance if carbon dioxideis the medium in which coal is entrained during milling.

The term “catalyst” as used herein refers to a first compound thatfacilitates the conversion of a second compound to a third compound, butwherein the catalyst is recovered substantially unchanged.

The term “catalyst precursor” as used herein refers to a substance thatis converted to a catalyst by conditions that occur in a process afterthe introduction of the catalyst precursor.

The term “absorbent” as used herein refers to a substance that traps orcaptures heteroatoms such as sulfur, nitrogen or oxygen atoms from thefuel. Examples of absorbents herein include carbon monoxide, calciumoxide, magnesium oxide, copper hydroxide, and zinc oxide.

The term “reducing agent” as used herein refers to a substance thatdonates electrons or hydrogen to a substrate compound. The terms“hydrogen donor,” “hydrogen-donating organic substance,” “substance thatcan serve as a source of hydrogen transfer,” and “molecular species thatis capable of donating one or more of its hydrogen atoms,” as usedherein are interchangeable and refer to a substance from which hydrogenis transferred to a substrate. These terms as used herein are notlimited by the state of the hydrogen when it is transferred, whether asmonatomic hydrogen radicals, protons, hydride anions, or complexedhydrogen.

The term “natural gas” as used herein refers to fossil fuel gases foundin nature including primarily methane but also other low alkanes andother compounds found in natural gas. The term natural gas as usedherein is not exclusive of synthetic mixtures that mimic the natural gasfound in nature.

The term “synthesis gas” or “syngas” as used herein refers to a mixtureof carbon monoxide and hydrogen gas.

The term “recycle oil” as used herein refers to oil that is reclaimedfrom a conversion process, for instance from liquefaction, and which isfurther used for another iteration of chemical conversion in the sameprocess or another conversion process. The term recycle oil as usedherein can be used interchangeably with another term of art in theindustry, “process-derived oil”.

The term “low alkane” refers to saturated hydrocarbons having up to fivecarbon atoms in their molecular formula.

The term “nickel steel” and “carbon steel” as used herein refers havetheir ordinary meaning in the art of mettalurgy.

The term “refractory” as used herein refers to materials and chemicalbonds that can withstand decomposition at high temperatures. Thusrefractory bonds resist reactions and cracking or hydrocracking. Withregard to combustion, the term “refractory” as used herein refers tobonds that require burn temperatures over 2600° F. With regard tocatalytic hydrocracking, the term “refractory” as used herein refers tobonds that require reaction temperatures over about 840° F. (450° C.) ata hydrogen gas reaction pressure of 500 psi in the presence ofhydrocracking catalysts.

The term “scrubber” as used herein refers to an in-line apparatus forcapturing gas-entrained solids as a suspension in a liquid medium, wherethe gas may be steam or another gas.

The term “scrub” as used herein refers to blowing steam effluent into aliquid medium in a scrubber.

The term “humid” as used herein refers to a gaseous atmosphere in whichwater vapor is present.

The term “combustion” as used herein refers to the burning of a fuel inthe presence of oxygen, in which the oxygen may be provided from air oranother source. With respect to fuels such as coal steam and naturalgas, the term “combustion” as used herein includes the conversion of thefuel to syngas during combustion, and subsequent burning of the syngas.

The term “in the presence of oxygen” refers to the availability ofdioxygen in the surrounding medium, whether in the form of air, otherdioxygen-containing gas, or dioxygen-containing liquid.

The term “gasification” as used herein refers to conversion of a solidor liquid carbonaceous fuel such as coal, petroleum or biomass intocarbon monoxide and hydrogen by reacting the raw material at hightemperatures; the resulting gas mixture is called “synthesis gas” or“syngas” and is itself a fuel. Whereas conventional gasification methodsrequire the presence of some oxygen (optionally from air) for oxidationduring gasification, the term “gasification” is not so limited when usedwith reference to the present invention.

The term “liquefaction” as used herein as used herein refers toconversion of a solid fuel into a liquid fuel such as gasoline, diesel,or other liquid hydrocarbon fuels. The term liquefaction as used hereinincludes both direct conversion of solid to liquid fuels, and indirectconversion whereby solid fuels are first gasified and then the gases arepolymerized to form liquid fuels. The term “direct coal liquefaction” orDCL as used herein refers to deconstruction of complex coalmacromolecules by heat, pressure, and catalytic hydrogenation. The term“indirect coal liquefaction” or ICL as used herein refers to coalgasification followed by polymerization of the gas to form liquid fuels.

The term “methanation” as used herein refers to catalytic processes thatconvert carbonaceous compounds to methane, including catalytic processesthat yields methane from syngas (i.e., carbon monoxide and hydrogen)starting material, whether in simultaneous or sequential reaction steps.

The term “dissolution” as used herein with respect to liquefactionrefers to the process of dissolving fuels by breaking their bonds toheteroatoms during reaction with carbon monoxide or another reducingcompound.

The term “heteroatom” as used herein has its ordinary meaning in organicchemistry, and for instance includes nitrogen, sulfur, and oxygen atoms.

The term “beneficiation” as used herein refers to removal of one or moreheteroatoms from a fuel solid composition, and or refers to the removalof ash, mercury or water from that composition.

The terms “suspension” and “slurry” as used herein refer to a suspensionof solids in a liquid medium, and are interchangeable. The termssuspension and slurry as used herein are not limited to a particulartype of liquid medium.

The term “oil suspension” as used herein refers to a suspension in whichthe liquid medium is hydrophobic such as a number 6 oil, recycle oil,donor solvents, and other hydrophobic media.

The term “aqueous suspension” as used herein refers to a suspension inwhich the liquid medium is primarily aqueous. The term aqueoussuspension as used herein includes both water-based suspensions, andalso includes suspensions of fuels in so-called “black liquor”containing high amounts of lignin and or related byproducts from papermill waste in addition to the suspended solid fuel.

The term “oil-&-water suspension” as used herein refers to a suspensionhaving substantial proportions of both water and hydrophobic substancescomprising the liquid media.

The term “stable” as used herein with respect to a suspension of solidsrefers to the substantial absence of precipitation of solids from thesuspension over a period of at least a week.

The term “surfactant” as used herein refers to a substance that is usedto prevent precipitation of solids in a suspension.

The term “black liquor” as used herein has its ordinary meaning in thepulp and paper industry.

The term “ambiphilic” as used herein refers to the property of surfacesbeing compatible with, that is able to remain suspended in, bothhydrophobic liquid media and hydrophilic liquid media.

The term “hydrophilic” as used herein refers to surfaces that permitwetting by aqueous media, or refers to non-aqueous liquid or gaseousmolecules that can be mixed with aqueous media in a uniform phase to asubstantial extent.

The term “hydrophobic” as used herein refers to surfaces that repelwetting by aqueous media, or refers to liquid or gaseous molecules thatcannot be mixed with aqueous media in a uniform phase to a substantialeffect.

The term “oleophilic” as used herein refers to surfaces that permitwetting by hydrophobic media, or refers to non-aqueous liquid or gaseousmolecules that can be mixed with hydrophobic media in a uniform phase toa substantial extent.

The term “coating” as used herein with respect to fuel particles refersto a deposit or dispersion on the surface of the fuel particles wherebya substance that is different from the fuel comprises a substantialamount of the coating, deposit or dispersion. Exemplary coatingsubstances include catalysts, catalyst precursors, and absorbents. Asused herein the term coating encompasses both adhered laminar coatingsand adhered particulate matter. The term “coating” as used hereinfurther contemplates deposits comprised of pure, mixed, blended, orlayered substances.

The terms “deposit” and “dispersion” as used herein are interchangeable,and refer to the distribution of a first substance onto a particle of asecond substance. The terms “deposit” and “dispersion” as used hereinneither indicate nor contraindicate adhesion or bonding between thedistributed first substance and the particle of the second substance.

The term “native coal” as used herein refers to coal in its originalstate as mined and without further treatment.

The term “carbonaceous infrastructure” as used herein with respect to afuel refers to the density of the non-volatile organic phaseirrespective of the presence of water or organic volatile substances inthe fuel. In other words, the density of the organic structure refers tothe density of structure associated with the fixed carbon.

The term “fixed carbon” as used herein refers to the carbon atoms in thecarbonaceous matter that remains after water and volatile componentshave been removed from a fuel solid.

The terms “volatiles” or “volatile matter” as used herein refer to thematerial in a fuel solid that may be removed by heating or solventextraction. With respect to coal, the terms “volatiles” or “volatilematter” as used herein have their standard meaning in that art. Forstandard volatilization test conditions, temperatures of 1640° F. (895°C.) to about 1785° F. (975° C.) are applied in the absence of air over aperiod of several minutes to remove volatile components except moisture,but these are not limiting temperatures for the term “volatiles” or“volatilization” as used herein; devolatilization commonly begins attemperatures as low as 600-700° F.

The term “porosity” as used herein with respect to a fuel refers to theporosity of the non-volatile organic phase irrespective of the presenceof water or organic volatile substances in the fuel. Porosity includesboth the volume of space in exposed pores at the surface as well as theinternal porosity and channels within a particle. To the extent that afuel particle's pores are collapsed in the absence of water or volatilesor where particles are crushed by grinding, the internal porosity isreduced and the volume of pores exposed at the surface may be reduced aswell. When the term porosity is used herein with respect to flow throughinterstitial spaces between neighboring particles, it refers to theinterstitial spaces between the particles.

The term “surface area” as used herein with respect to a fuel refers tothe surface area of the non-volatile organic phase irrespective of thepresence of water or organic volatile substances in the fuel. The termincludes the area of organic phase surfaces internal to fuel solids. Forfuel solids whose phases collapse in the absence of water or volatilesor where particles are crushed by grinding, the internal surface areasare reduced.

The term “interface” as used herein with the surface area of a fuelsolid refers to the region of the fuel solid that is immediatelyphysically adjacent to and juxtaposed with a secondary substance.

The term “covered” as used herein with respect to the surface area of afuel solid refers to the area of the fuel solid that has a directinterface with a secondary substance. Where a secondary substance isembedded in a fuel solid, the term “covered” refers to the cross-sectiondefined by the outer perimeter where the fuel solid and secondarysubstance meet, as opposed to the three-dimensional interface betweenthe fuel and secondary substance in the embedded region.

The term “eclipsed” as used herein with respect to the surface area of afuel solid refers to the area of the fuel solid that is directly beneatha deposited secondary substance though that portion of a particle ofsecondary substance may not be in actual contact. By way of analogy, ifa surface of a fuel solid is illuminated from a perpendicular direction,the eclipsed region would be the portion of fuel surface that is in theshadow of deposited secondary substance but does not have an actualinterface with the secondary substance there. As defined herein, thecombination of covered and eclipsed surface area for a secondarysubstance on a fuel solid represent the full extent of dispersion of thesecondary substance on a fuel solid surface.

The term “surface” as used herein refers to the outer boundary of asolid or liquid composition, or to a layer constituting or resemblingsuch a boundary. The term “external surface” as used herein with respectto a particle, refers to the surfaces at its exterior, as opposed to thesurface of a pore within the particle, which is referred to herein as an“internal surface”. Where channels, pores or other void spaces permeatea particle and are visible within it, the external surface is defined toinclude all surfaces at the outermost faces of the particle, but notsurfaces that define the channels, pores or other void spaces.

The term “cracking” or “hydrocracking” as used herein refers to the useof high temperatures and or hydrogen gas pressures to break largermolecules into smaller molecules

The term “refractory organic bond” refers to a bond in an organicmolecule that cannot be hydrogenated at conventional liquefaction orgasification temperatures, or which require temperatures of 2600° F. ormore for combustion.

The term “coal body” as used herein refers to a particulate coal solid.The term “coal body surface” as used herein refers to interior andexterior surfaces of the coal body. For example, a coal body withinternal pores would have coal body surfaces at the boundaries of thosepores, though the pores may be isolated.

The term “hydration layer” as used herein refers to thin layers of wateron interior and or exterior surfaces of a fuel solid.

The term “ambiphilic hydration layer” as used herein refers to ahydration layer that is distributed on a fuel solid surface in a mannerthat permits the fuel solid to form stable associations with hydrophilicliquid media and with hydrophobic or oleophilic liquid media, such thatthe fuel solids may form stable suspensions in either type of medium.The term “ambiphilic hydration layer” does not connote that the watermolecules in the hydration layer are themselves necessarily responsiblefor the hydrophobic or oleophilic character of the hydrated fuel solidsurface.

The term “molecular monolayer” as used herein refers to a layer of asubstance one molecule thick on the surface of a solid.

The term “solvation layer” as used herein refers to a layer of solventmolecules which form an oriented or quasi-oriented array in associationwith a hydration layer. That is, the hydration layer would be sandwichedon one side by a solid fuel surface and on the other by a solvationlayer. The term solvation layer herein may refer to a hydrophilicspecies such as water molecules, or such as a hydrophobic species suchas oil molecules.

The term “reactive site” as used herein refers to a molecular feature ona solid fuel surface which is particularly amenable to combustionreactions and or to other chemical conversion.

The terms “aggregation” and “agglomeration” as used herein aresynonymous and refer to an ongoing physical association between two ormore particles.

The term “adsorb” as used herein refers to the formation of a stablephysical association between a substance and the surface of a solid.

Theory Behind the Discovery and Invention

It has been discovered unexpectedly that a certain process and itspermutations provide solid fuel particles that have remarkableproperties. For instance, cleanly broken surfaces are provided, which inthe absence of atmospheric contamination, and in combination with asurface hydration layer, impart several unusual but highly usefulcharacteristics to these fuels. For instance, anhydrous fuel particlesfrom the invention that are rehydrated at their surfaces lose theirtendency to aggregate. Such particles also show an ability to remainstably suspended in both hydrophobic liquid media and hydrophilic liquidmedia. The microparticles that have been created this way and are eitherentrained in steam or protected by it with hydration layers undergocombustion at lower temperatures and thus avoid thermal formation ofnitrogen oxides from dinitrogen in the ambient atmosphere, in fact whensuspended in steam their flame is colorless, transparent and clean inappearance like that of natural gas. Likewise, microparticles havinghydration layers are converted more readily to alternative fuels byliquefaction or gasification. Micronized fuels that have been createdand protected with hydration layers also burn and otherwise react moreuniformly than do comparable fuels lacking such layers. The hydrationlayers also aid in coating solid fuels with catalysts and othercompounds. The hydration layers appear to be most effective when theyare formed on solid fuel surfaces on which dioxygen has not had a chanceto adsorb or react.

Without being bound by theory, an explanation in this and followingparagraphs is offered to rationalize these various phenomena. Ordinarygrinding of solid fuels such as coals (such as “standard pulverizedcoal” (SPC)) and such as resinous wood results in crushing of theirnative structure, collapsing or sealing the internal pores irreversibly,reducing the surface area available for chemical reactions. Thatcrushing also squeezes oils and tars out of pores and smears them on theparticle surfaces, making them hydrophobic. The crushing also produces“mechanochemistry,” in which shearing of molecular structure producesorganic radicals at newly exposed surfaces. Some of these radicals formrefractory bonds by recombination, for instance when aryl radicalscombine; such aryl-aryl bonds are usually not present in most organicsolid fuels such as coal, and they can also result in covalently-heldaggregation between particles. Others of these radicals candisproportionate to form refractory bonds. Where electron transfer orother charge transfer occurs upon impact, static charge fields may form,causing aggregation of particles. And the radicals can react withatmospheric oxygen to form peroxides and other unstable compounds,resulting in extensive cross-linking of the structure, refractorythree-dimensional networks in the fuel, and refractory carbon-oxygenbonds at the surfaces. Some abstraction of hydrogen atoms is alsoexpected from reaction by these radicals. Because the refractory bondsrequire elevated temperatures for burning, cracking or other chemicalconversions, such fuels cannot be used efficiently except at hightemperatures and or high pressures. The high temperatures, in turn, areassociated with a drop in process economies, and with further increasesin refractory properties because of slow heat transfer through the bulkof a particle.

By contrast, the effectiveness of the current method is rationalized inpart by noting the velocities of the invention method. The particlemomentum at impact is believed to impart kinetic energy at such a highvelocity than it cannot be defused on the time scale of an elasticdeformation of pore walls, or by the viscous flow of tar-like so-called“volatiles” that are found in coal. Thus instead of a collapse of poresthroughout the material, and instead of the displacement of tars andconsequent filling of pores as might occur in conventional grinding, itis believed the walls of the pores nearest to the impact point aresimply shattered or sheared in the invention method. The breakage isbelieved to be further aided by the superheat of the steam medium used:by analogy to popcorn, this is believed to cause water-filled pores toexplode as the internal water is rapidly heated well past its boilingpoint. Such steam explosion is also believed to expand nano-fissures inthe materials to produce new or significantly enlarged pores. Normallythe internal heating would be relatively slow, however heat transfer tothe interior of fuel solids can be extremely rapid for particles havingsub-millimeter diameters such as those generated within the mill.

And again without being bound by theory, the anaerobic conditionspresent in the mill and the hydration layers formed there are hereinbelieved to shield radicals formed at solid fuel surfaces during andafter grinding. This shielding minimizes the tendency for radicals tocombine with dioxygen. That in turn reduces the tendency of fuel solidsto form internal cross-links and thus eliminates one mechanism forporosity reduction during grinding. The water is further believed todissipate the effect of any static charge that builds up.

By retaining much more of the native porosity and internal and externalsurface area of the fuel solids, and by expanding it, the presentinvention is believed to offer a greater surface area for combustion,cracking, and other chemical reactions. The internal porosity of coal isthought to have as much as 100-1000 times as much surface area as theexternal surface, thus this is a non-trivial advantage. High surfaceareas enable faster and more uniform consumption of the fuel duringthese reactions, and also enable a more consistent and efficienttransfer of energy to and from the solid particles during thesereactions. The efficiency of heat transfer and the substantial absenceof refractory bonds also allows the improved fuel solids to be consumedat lower temperatures, thereby avoiding, for instance, undesirablethermal formation of nitrogen oxide compounds from atmosphericdinitrogen.

The ambiphilic nature of fuel particles provided by the invention methodis attributed to the clean breakage of the fuel solid such that bothhydrophilic coal surfaces and hydrophobic oils and tars in exposed poresare presented at the external surfaces of the comminuted particles. Useof hydration layers breaks up aggregates and aids in suspension. Thusfor materials such as coal or resinous wood substances such as pine, theexternal surfaces of comminuted particles obtained from the inventionprocess represent a combination of zones. Surface zones of hydrationlayers deposited directly on the wood or carbonaceous infrastructure ofcoal alternate with and are complemented by surface zones of unhydratedtar-like volatiles, thus both hydrophilic and oleophilic externalsurfaces are presented, resulting in the ambiphilic character. Thecharacteristics of the surface and its hydration layers are alsobelieved to be responsible for the improved adhesion of fuel solids tocatalysts, absorbents, and other coating compositions. However theinvention is not limited by the molecular origin of the hydrationlayers' properties. Hydration layers also hinder the adsorption ofoxygen to fuel surfaces, and thus slow the chemical oxidativedegradation of such surfaces.

Ordinarily surfactants must be used to obtain this level of affinitybetween solid fuel surfaces and liquid media. The ambiphilic surfacesand their hydration layers' affinity for liquid media enables theomission of surfactants in solutions, which represents a significantadvance. Not only do surfactants represent an extra materials cost infuel use, but in many cases they bind to the active sites on fuelsurfaces, thereby impeding combustion and catalytic activity. It isbelieved here that the omission of surfactants is an additional reasonthat the fuels of the invention are particularly effective.

As an added benefit, suspensions obtained through the invention haveproved to be particularly beneficial in high velocity flow applicationsbecause they cause little or no wear on nozzles or other parts. Thistribological property is believed to have its origins in a synergisticcombination of the small particle size and in lubrication effects by thesolvation layers on the particle surfaces, with the result that theparticles cause much less turbulence in fluid dynamics, as well as muchless friction. The salvation layers are believed to be substantially orentirely comprised of water molecules, and to form during theorganization or quasi-organization of liquid media about the particleswhen the suspension is created.

Thus a series of complex interrelated working hypotheses about thechemical and physical mechanisms have rationalized the discoveries andguided the invention disclosed herein. Nevertheless the metes and boundsof the invention are not defined by the theory.

Comminution Apparatus

It has been found that for purposes of this invention comminution offuel solids proceeds most effectively at high speeds and when thepresence of molecular dioxygen is reduced or substantially excluded. Ithas further been found that protection of the comminuted particlesagainst dioxygen is beneficial at least to the point where hydrationlayers are formed, and even up to the point of the end use for thepowder. The present invention provides improved steam-driven jet millsand an improved jet milling processes. Prior steam-driven jet mills aredisclosed in a series of turbine patents to Taylor et al., see U.S. Pat.Nos. 3,978,657; 4,164,124; 4,288,231; 4,394,132; and 4,412,839, thecontents of which are incorporated herein by reference. Also known asfluid energy attrition mills (FEAMs), jet mills in the prior art haveroutinely processed as much as 20 tons of coal per hour, with feed coalcontaining 6% to 30% or more water and 10-20% ash. Typically theseoperations have been used to produce coal materials with a top particlesize of about 40 microns and an average particle size of 20 to 25microns; usually no minimum particle size is specified. Older designs ofjet mills relied intentionally or incidentally on collision between theparticles and mill housing, resulting in extreme wear. Examples includemodels from Micro Energy Systems and Fluid Energy Products. By contrast,FEAMs use the shear field to grind the coal, thereby avoiding wear onthe housing.

Fluid energy attrition mills as a class provide a shear field between aslow-velocity outer zone of gaseous medium and rapid-velocity inner zoneof gaseous medium. The gas can be any gas, but the properties and costof steam make it particularly useful for these mills. The spiral flow ofgas for the shear field is obtained by directing a series of nozzles atangles relative to one another; a housing keeps the steam flow cyclicalso that the momentum is not dissipated by centrifugal flow. Vortexshedding from the shear field rotates particles cyclically out of andback into the shear field where they are fractured by collisions,thermal cycles, and steam impact. The larger particles drop back intothe grinding field and are re-mixed with the grinding steam. The shearfield grinds the coal, whereas the vortexes classify the coal;micronized particles are carried upward away from the (typically)horizontal grinding field and vented with the steam. Typically but notnecessarily the nozzles are located in a coplanar fashion just above thebase of a vertically oriented mill. Typically but not necessarily thenozzles are located at regular intervals about a circle. Spray from thenozzles is typically but not necessarily directed somewhat upward fromthe base, e.g., about 12.5 degrees, and somewhat askew from therespective directions of spray of the next nozzle and previous nozzle inthe circular series. The upward component of the nozzle angle determinesthe number of rotations per vertical unit distance in the upward spiralof steam. In one embodiment the spray defines a cone with about a25-degree angle between the opposite edges of the cone as measured fromthe nozzle. Vortices are shed when the high velocity of the ejectedsteam from the nozzle intercepts the recirculation stream at theperimeter of the reaction vessel's interior, which is relativelyquiescent. Thus in that embodiment a 12.5-degree angle of skew from onenozzle's direction to the direction of the next nozzle is particularlybeneficial, though skew angles can differ by 10 degrees or more fromthat relative orientation. The skew angle is important regarding anglinginto the quiescent stream, and for imposing uniform rotational flow.

Angles that differ by more than 2 or 3 degrees from the ideal12.5-degrees are often complemented by baffle or plug mechanicalfeatures in order to bring the aerodynamic flow closer to ideal,otherwise it can lead in some cases to “burping” of fines when theyreach a critical mass. The skew angles from the coplanar base and fromthe radius do not need to be identical. In one embodiment the skewangles relative to the base and or the other nozzles are between 2.5 and22.5 degrees. In another embodiment they are between 7.5 and 17.5degrees. In another they are between 9.5 and 15.5 degrees. In stillanother they are between 10.5 and 14.5 degrees. In still another theyare between 11 and 14 degrees. In a further embodiment they are between12 and 13 degrees. In another embodiment they are approximately 12.5degrees. A small gain in efficiency can be achieved if the nozzles arearranged such that the circular flow of steam that they provide isconsistent with the direction of Coriolis force, i.e., counterclockwisein the northern hemisphere, and clockwise in the southern hemisphere.

In order to achieve rapid comminution, the steam velocity at the nozzleneeds to be high. Sonic velocities are the highest practical velocities;above that point shock waves dissipate the energy without contributingto laminar flow and slow the speed to the sonic or subsonic level, thusthe supersonic margin of energy is wasted. In air sonic velocity is ca.1130 ft/s, however in steam the sonic velocity is ca. 2014 ft/s, thussteam provides a particularly effective shear field and vortex mediumfor achieving rapid grinding. The velocities are achieved bydecompression of pressurized steam; the steam expansion ratio determinesthe velocity. Where a steam nozzle provides an expansion ratio of ca.1.818:1 (i.e., the reciprocal of 0.55) in the throat of the nozzle,sonic velocity is achieved. However useful grinding velocities can beachieved with lower expansion ratios, for instance, at 1.5:1, whichprovides a steam speed of about 1340 ft/s. Subsonic velocities result inlower shear and vortex speeds, less flow energy, faster energydissipation in the shear field and vortexes, thereby reducing thegrinding capacity, and providing less efficient classification of theparticles. Thus in one embodiment the gas injection velocity is 0.5 to1.0 times sonic velocity, and in another embodiment 1.0× sonic velocityis used. Sonic speed is a function of the square root of the molecularmass of the gas used; by way of comparison, water in steam has amolecular mass of ca. 18, dinitrogen gas has a molecular mass of ca. 28,carbon dioxide gas has a molecular mass of ca. 44. Based on the squareroot relationship the sonic velocity of carbon dioxide will be just over50% higher than for steam.

The axial length of the milling chamber is also a factor in thecomminution specifications, because particles require a critical numberand kinetic energy of impacts with each other in order to reach thetargeted small sizes. In one embodiment the length of the reactionchamber—and thus the axial length of the shear field and steam vortexesfor classification—is selected empirically. In another embodiment thelength is selected to allow particles to travel for an average of atleast 10 revolutions or at least 10 seconds before exiting the chamber.

Illustrative production-scale mills of this type may employ 60 nozzlesin a housing diameter of 5 feet, and a housing length of 1-12 feet, andcomminute 40,000 lbs. of ¼″×0 nuggets of coal per hour to a maximumdiameter of 40 microns. Smaller mills of the Stephanoff type (i.e., withcollision against the mill housing) have existed, with maximum capacityof 2 tons per hour, however they suffer from severe wear and cannot bescaled up. Smaller mills of the Taylor type (i.e., FEAMs) have not beenused or considered feasible in the prior art, however the presentinvention includes smaller mills, for instance using 6 nozzles in ahousing diameter of 24″, height of 36″, and grinding 300-600 lbs. ofcoal per hour with specifications otherwise similar to those of thelarger mills, though steam requirements and nozzle diameters change withcapacity. Exemplary dimensions for the smaller mills include nozzleswith a 9/64″ orifice, and a 32-inch vertical height for the mill. Thefigure of merit for the flow rate versus the vessel size is determinedempirically. The prior work by Stephanoff employed a toroidalconfiguration, processing 2 tons of coal per hour, and suffered fromwear problems where 500 lbs./hr steam eroded the walls of the vesselwhere they were within 60 inches of the steam injection jet. Theefficiency of fluid energy attrition mills that avoid particlecollisions against walls is a function of the amount of vortex shedding.The intensity of the vortex determines the classification—i.e., thesorting by size—of the coal particles. Higher vortex intensities enablesmaller particles to be produced.

The most convenient milling medium in many circumstances is steam, thusthe exemplary embodiments below describe use with steam, however othermilling media can be employed using specification adaptations that willbe apparent to persons of ordinary skill in the art. In one embodimentthe alternative medium is carbon dioxide, wherein after the coal ismilled in a medium comprising carbon dioxide moisture is added asnecessary to achieve the desired levels of hydration. Carbon dioxide isalso an attractive medium because it can be harvested from ordinary airand stored until needed; from such a source releasing it back to theatmosphere causes no net change in the environmental carbon fingerprintof the milling facility.

As for the embodiments that use steam as the milling medium, the steamis superheated. In a representative embodiment the steam is provided atthe source from a boiler that provides 750° F. (400° C.) super-heatedsteam at 200 to 650 psi. Upon expansion to ambient pressure when leavingthe nozzle at the bottom of the drum (i.e., at the bottom inside thecomminution chamber), and also due to contact with the lower temperaturefuel solids, the steam temperatures typically fall to 225° F. (110° C.)in the chamber, still superheated but less so, and now usually atapproximately atmospheric pressure. At a two-fold expansion the steam isinjected at sonic velocity; the internal velocity of the mill is thenproportional to the drum size.

The mill may employ a single-walled design, such that the same layer ofmetal that constrains the shear field and vortexes also serves as anexterior wall of the mill. Or the mill may have more than one wall, suchthat there is an internal wall defining the reaction chamber andconstraining the steam, and a separate external wall.

The fuel solids are entrained in the steam. A particularly convenientapproach is to begin with nuggets that are ⅛″×0 to ½″×0 in size; forfuels such as coal this is not an unusual specification. However, themill can also comminute nuggets with diameters as high as 3 to 4 inches;this depends in part upon the density of the solids. Because theparticles are different sizes they move with different velocities anddirections and collide en route. As the nuggets are ground, thecentrifugal force on the pieces becomes less due to their decreasingmass, and the micronized particles migrate to the center and top of thechamber, from which the steam is vented by an output feature. Themicronized particles are collected from the vented steam either bydrying or by passing the spent steam through a scrubbing unit whichscrubs the steam in a liquid medium to capture the particles in asuspension or conveyed in the entraining steam to a boiler. The outputfeature may also or alternatively be in line with a gasifier unit or aliquefier unit.

Fuel solids can be entrained in the steam by any of several means whichare familiar to persons of ordinary skill in the art. For instance, inbatch processing the entire amount of fuel solids can be present in themill and introduced by gravity feed from a hopper into steam near theonset of the shear field. However it is generally more useful to have acontinuous feed of fuel solids into the mill, for instance with a screwfeeder introducing fuel solids from the outside to the inside of thegrinding chamber. By using an optional steam jacket about the screwfeeder, oxygen can be excluded more completely and the fuel solids canbe injected into the mill with more force.

In the prior art, jet mills used for coal with superheated steam haveimparted enough heat to the comminuted coal to drive evaporation tocompletion when the steam was vented; the resulting particles were thenused in an essentially anhydrous state for combustion, and withoutprotection from oxygen. However it has now been discovered that thepresence of a hydration layer substantially improves the fuel particles,particularly where oxygen has been excluded. Mills adapted for thispurpose control the steam conditions so that a small amount of waterremains present to hydrate the comminuted fuel surfaces; severalillustrative embodiments demonstrate this. About 0.25% to about 5.0%water by weight relative to the fuel solids is generally adequate forcreating a hydration layer. The precise extent of hydration in theresulting fuel will depend on several factors including the design ofthe mill, but some illustrative values are provided here.

In one embodiment the mill has a governor that caps or raises the steamtemperature and or its rate of injection into the reactor. The governoris set at a level that leaves the steam-entrained fuel solids with alevel of heat to enable evaporation of water from the fuel to a desiredlevel upon venting from the reactor or during the scrubbing step. Forexample, for 30,000 pounds of steam containing 40,000 pounds of fuel,the steam is provided at about 750° F. (400° C.) at the point ofinjection, falling to about 300° F. (150° C.) due to heat dissipationduring particle comminution. The typical ten-second dwell time of coalin the mill during processing represents an estimated 111 pounds of fueland 83 pounds of steam. After venting the steam-entrained fuel solidsthe weight percent of water remaining in the particles after evaporationof the steam depends on the fuel's initial water weight. For instance,superheated 750° F. steam at 200 psi at the source can provide enoughheat to evaporate coal with up to about 12% initial moisture to bonedryness, can remove all but about 2.5% moisture from coal containing 15%moisture initially, and for the next several increments of humidityleaves 5% of moisture in the final coal for each additional 4% ofmoisture it contains initially, by weight. The reason for the fallingability to dry coal is that larger quantities of energy from thesuperheated steam are lost when heating the moisture of very wet fuel tothe 300° F. temperature inside the mill before venting. Lower steamtemperatures have correspondingly lower capacity to dry the coal, thusunder otherwise analogous conditions, steam that has 650° F. (ca. 345°C.) and 200 psi at the source provides enough heat to evaporate coalwith no more than about 9% initial moisture to bone dryness.

In another embodiment a cool-water spraying unit is placed inside thereaction chamber near the vent. The cool water is provided in sufficientquantities and with a low enough temperature to reduce the heat contentof the exiting steam below the point where it will evaporate to leavecomminuted fuels anhydrous. The heat capacity of water and thus itscooling effect are calculable for any desired level of cooling. In yetanother embodiment cool water is provided by a misting unit just outsidethe steam vent to cool the exiting steam.

In locales where water resources are particularly limited or costly, thesteam can be recaptured by condensation after milling, and any waterremoved from the coal before milling can also be recycled. Because thewater content in native coal may represent 30-40% by weight, mere use ofthe coal provides a constant source of new water as a resource. Coalvarieties that are particularly high in moisture include low-sulfursubbituminous and lignite coals from North Dakota, Wyoming and Montana.

In another embodiment a steam spraying unit is placed inside thereaction chamber near the vent. The steam or super-heated steam isprovided in sufficient quantities and with a high enough temperature toincrease the heat content of the exiting steam below the point where itwill evaporate to a desired dehydration level for the comminuted fuel.In a further embodiment steam or super-heated steam is provided by aspraying unit just outside the steam vent to heat the exiting steam orafter initial evaporation, the comminuted fuel.

In another embodiment a steam jacket or super-heated steam jacket iscombined with a screw feeder for fuel entering the processor. The steamis provided in sufficient quantities and with a high enough temperatureto in order to evaporate initial water in the fuel to a desired levelprior to comminution.

In still another embodiment, the mill is in line with an evaporationunit from which steam is allowed to evaporate from the issuing flow fromthe mill in the absence of dioxygen, and where the anhydrous or mostlydry fuel is rehydrated. The rehydration may for instance be carried outby a misting unit, a steaming unit, or a sub-saturation humidifyingunit. The rehydration may also be conducted by adding moisture to a fuelsolids-in-oil suspension, for instance adding 2.5% water by weight offuel solids in the suspension.

Optional but desirable features in the mill include means forintroducing within the chamber a secondary substance such as a grindingaid, catalyst, catalyst precursor, absorbent, hydrogen donatingsubstance or other reducing agent, or other substance. In some cases thesecondary substance is most conveniently introduced by adding it to ormixing it in solid form with nuggets of fuel, or by spraying the nuggetswith a solution or suspension containing the secondary substance. Inother cases the secondary substance is most easily introduced by meansof an ancillary feeding device, such as a hopper, screw feeder, or byinjecting it through the nozzles along with the steam jets that form theshear field and vortexes. Optionally, in addition to an inlet for steamor another driving gas the mill has also or in the alternative an inletfor a secondary substance which is an added gas such as natural gas,hydrogen gas, carbon monoxide, carbon dioxide, methane, syngas, steam,or another gas or gaseous mixture.

The internal surfaces of the reaction chamber must be able to withstandthe temperatures generated by the presence of superheated steam in theabsence of oxygen. For these typically nickel steel, carbon steel andrefractory ceramics are adequate, particularly since the fluid energyattrition mill design avoids wear by the fuel solids on the mechanicalparts. Essentially all of the grinding is conducted in the steam shearfield. Higher temperatures can be accommodated in the reaction chamberas necessary, for instance where a fuel surface is being coated with orreacted with a reducing agent or catalytic substance. Thus thermallyinsulating features such as mantles, thermal blankets, inserts,refractory tiles and the like can be used to protect the interiorsurface of the wall of the reaction chamber to 1200° F. (650° C.), 1600°F. (870° C.), or higher. For reactions in which no more than severalatmospheres of pressure are being applied, a steel-walled orceramic-walled reaction chamber often will need no additionalprotection. It is noted here that corrosive substances such as causticcompounds may not be compatible with a particular ceramic, and thatalumina, silica and titania compositions are susceptible to degradationby gasification catalysts in particular. Thus metal or othernon-reactive coatings on these ceramics are necessary if they will beexposed to corrosive compounds.

Comminution Process

Using an apparatus such as the one disclosed above, or using anapparatus that performs similar functions, fuel particles can becomminuted and provided with hydration layers. The fuel solids may be ofany type; examples include coal varieties such as lignite, bituminous,subbitumionous, anthracite and peat, as well as other carbonaceousmaterials such as cokes, including petroleum cokes, and biomass. Whenanthracite is used, the milling process or a subsequent step mustinclude extra capacity to hydrogenate the material because of the lowhydrogen content in the coal Alternatively or in addition the fuelsolids may include biomass such as peat (which is both coal-like andbiomass-like), sawdust, wood, pulp, paper, straw, lignin, chaff,bagasse, agricultural waste, forest waste, yard waste, mulch, microbialbiomass, fishery waste, feathers, fur, hoofs, manure, and so forth.Alternatively or in addition the fuel may be petroleum coke.

Also alternatively or in addition the fuel solids may include syntheticpolymers including but not limited to polyolefins such as low- andhigh-density polyethylene, polypropylene, and polybutylene; vinylpolymers such as acrylic and methacrylic polymers and polystyrene andpolyvinylchloride; rubbers such as natural and synthetic polyisoprenerubbers and latexes, as well as acrylonitrile-butadiene-styrene (ABSpolymers), alkyl silicones and other synthetic rubbers; ring-openedpolymers such as polyalkylene oxides; epoxides; condensation polymerssuch as polyethers, polyetheresters, polyamides such as nylons, andpolyesters including phthalate polymers such aspoly(ethyleneterephthalate); and other synthetic polymers such as areknown to persons of ordinary skill in the polymer arts.

Particularly where the fuel is soft or fibrous such as peat or plantfiber, or where the fuel is molten at the working temperatures of theinvention process conditions, it can be useful though not absolutelynecessary when grinding to include a hard grit or a hard fuel materialthat is not molten under the process conditions. Ordinarily mills willnot grind soft, fibrous or molten materials, and yet such materials canbe excellent fuels especially after comminution. Thus the currentinvention is not limited to hard fuels.

Fuel solids are provided usually ⅛″×0 to ½″×0 in maximum diameter in oneembodiment, however they can be up to 3 inches in another embodiment,provided that the solids are ground for a sufficient period of time andat a sufficient level of energy to reach the targeted degree ofmicronization. Typically any fuel solid that has already been partiallycomminuted by a hammer mill is satisfactory as a starting material.Pieces of petroleum coke used in the mill can be larger than those ofmost other types of fuel because it is a friable material, e.g. 5 inchesor more in widest diameter is viable if the supply mechanism for themill can handle pieces that size.

A useful size range for starting material in grinding coal is ⅛″ to ½″×0mesh size, and ¼″×0 mesh size is particularly useful, however theinvention is not so limited. Typically larger pieces of coal arecrushed, as in a hammer mill, and then screened on a grate to reach thatparticle size. The small coal can be fed through a surge hopper andinjected into an aerodynamic grinder with one or more jets ofsuper-heated steam to provide an approximately 1:1 mixture of coal andsteam by weight in a largely oxygen-free environment inside the grinder.The aerodynamic grinder referred to here is also known as a fluid energyattrition mill, and is an economical device to process large tonnagerates of material throughput.

The output is a stream of ≦40 micron diameter coal particles whoseparticle sizes tend to conform to a bell-shaped distribution curve,e.g., 10-40 microns in size though the maximum diameter can be smallerby allowing the particles to be ground for longer times they can be madesmaller still. An advantage of comminuting to smaller final particlesfor materials such as coal is that a larger proportion of heteroatomimpurities are exposed. This facilitates beneficiation, thus oxygen,nitrogen and sulfur moieties can be removed more efficiently if, forinstance, carbon monoxide is included in the steam during milling. Onefurther advantage of the method is that the particles are very porous,with channels running through them created in part by steam explosion ofsealed pores. And aerodynamic grinding is believed to be the method mostlikely to result in spherical particles, which have lower friction insuspension than non-spherical particles. By contrast, it has long beenrecognized that mechanical milling closes porosity by a combination ofcrushing the channels, agglomerating larger particles, and cloggingpores in large particles with small particles.

Another advantage of the method is that it can minimize the presence ofair during grinding. Academic literature has reported grinding underwater or in an inert atmosphere to keep air out. Here, injection of thesteam can be used to drive out any air in the grinding chamber beforethe coal is added, and also to drive out adventitious air from the coalbefore it is provided through a feeder such as a surge hopper. The priorart made no special provisions to exclude the air from productiongrinders; in fact, prior workers deliberately injected air into theirproduction-scale grinders. The primary factors in grinding include theamount of moisture in the coal, the beginning size of the coalparticles, the final desired size of the coal, the absence of air, andthe aerodynamics of the flow field. The fluid energy attrition mill ofthe invention typically employs ratios of 0.75:1 to 1.25:1 for thesteam:coal ratio by mass. Moisture already present in the coal affectsthe heating rate of the particles, the amount of steam necessary to heatthe coal, and is believed to produce a “popcorn” effect as it rapidlyreaches its boiling point within coal pores. The initial coal particlesize is important because larger pieces need more steam to drive themaround the shear field of the processor and to achieve an equilibrium ata desired temperature range within the coal particle itself. The desiredfinal coal size also affects the choice of parameters, because achievingfiner grinding requires extra circuits within the processor and thusextra steam. Typically a maximum particle size of 40 microns is providedby about 10 circuits within the shear field of the fluid attrition mill.

It is useful but not absolutely necessary to de-aerate the fuel solidsbefore milling them by the invention method. The de-aeration can be doneby treating them with essentially pure steam and or a gas such as carbondioxide or carbon monoxide prior to adding the solids to the reactionchamber.

In one embodiment, steam is provided at a temperature of at least 350°F. and atmospheric pressure. In another embodiment the steam is providedat 400° F. or more. In a further embodiment the steam is provided at atemperature of at least 500° F. In yet another embodiment the steam isprovided at a temperature of at least 650° F. In a further embodimentthe steam is provided at a temperature of 650-750° F. and 200 psipressure.

The rate of steam flow through a nozzle may be calculated in pounds persecond as 51.43× throat area of nozzle (in square inches)×manifoldpressure (in pounds per square inch). The critical (i.e., sonic)velocity is reached when the pressure on the steam exit side of thenozzle is 55% of the pressure on the steam entry side of the nozzle,e.g., when the pressure is 100 psi on the entry side and 55 psi on theexit side. And for instance sonic velocity in steam is reached when theenthalpy change falls from about 1380 to about 1300 BTU/lb of steam.After exiting the throat the steam will expand further to the pressurein mill, about 20 psi when it is operated at atmospheric pressure, atwhich point enthalpy is 1207. 1300−1207=93 BTU/lb steam contributed tothe grinding field, leaving 60 BTU/lb. in the steam before condensation;that 60 BTU/lb. is available to evaporate excess moisture. The entireenthalpy is thus 1380−1207=173 BTU/lb. which will evaporate nativemoisture from the coal or other fuel and heat it to the equilibriumtemperature in the mill. The exit temperature for a processor handling20 tons per hour is typically 200-300° F., depending on the moisture ofthe fuel solids at the outset. The square root of the steam's number ofBTU/lb. is multiplied by 223.8 ft/s to calculate the velocity of thesteam through a nozzle with a 1.818 decompression ratio when the sourcesteam has been held at 200 psi. Examples 1, 2 and 3 and FIGS. 1, 2 and 3provide additional illustrative calculations for the steam-driven dryingof coal.

A velocity within 5% of 1340 ft/s is on the low end of what iseffective; about 2014 ft/s is the optimum velocity in terms of energyefficiency, being the sonic velocity of dry steam. In one embodiment thesteam is provided at a velocity within 5% of 2014 ft/s; in anotherembodiment the steam is provided at a velocity within 10% of 2014 ft/s.In a further embodiment the steam is provided at a velocity within 20%of 2014 ft/s. In still another embodiment the steam is provided at avelocity within 30% of 2014 ft/s. In another embodiment the steam isprovided at a velocity within 35% of 2014 ft/s. Note that sonic velocityin steam differs from sonic speed in many other media: In dry air at atemperature of 70° F. (21° C.) the speed of sound is 1130 ft/s (344 m/s,1230 km/h, or 770 mph).

The steam is directed from a plurality of nozzles to form a shear fieldin a reaction chamber; the fuel nuggets are simultaneously orsubsequently entrained within the field and comminuted until the maximumparticle size is 40 microns or less. Distributions with 20- or 30-micronmaximum particle sizes are also convenient. Distributions with maximumparticle sizes as low as 10 microns are feasible. The comminuteddistributions have some polydispersity in size, i.e., they have adistribution of particle sizes with a statistical maximum at about themean particle size, however the particle size distributions can be muchnarrower than those of other FEAM or normal grinding methods. There is,however, no requirement that the fuel solid nuggets be polydisperse insize. There are also no chemical composition limitations on the inputparticles.

The steam provides a quiescent field outside the nozzle injection range,and a shear field and vortex shedding at the boundary between thequiescent and direct jet stream. The shear field is where most of thecomminution of particles takes place. In one size reduction mechanism,the larger particles are believed to have more inertia and thus haveless acceleration; thus the smaller particles accelerate more rapidlyand essentially erode the larger particles upon impingement. In anothersize reduction mechanism, steam pressure is thought to erode theparticles. In a third size reduction mechanism, a “popcorn” effect isthought to explode coal and other water-containing fuel particles whentheir internal water reaches the boiling point. In any case the largerparticles migrate to the outside of the centrifugal field, and thesmaller particles migrate to the interior of the centrifugal field andare collected there. The final particles are compared to popcorn (i.e.,porous compared to the starting material) as opposed to the “cornflake”-like coal particles (densified compared to the starting material)obtained from ball mills and other mechanical milling devices.

Some observations about the fluid attrition mill merit consideration.First, steam pressure can be reduced to control shearing properties.Also, only available superheat can be used to dry the coal. Superheat isthe excess of heat above the boiling point of water, which is 212° F. atambient pressure; for instance steam at 250° F. represents only about38° F. of superheat. The super-heated steam which entered the drum at650° F., exchanges heat and momentum with the coal and its waterinclusions, and retains only about 250° F. worth of superheat energy fordrying the comminuted fuel. 60 nozzles grind about 20 tons of ¼″×0 meshsize coal per hour. In an exemplary embodiment, one-quarter-inch nozzlesproduce about 500 pounds of steam per hour; using 3/16″ nozzles cutsthat steam velocity by about 50%. Supplying 400 pounds of steam pressurefrom the boiler instead of 700 pounds also cuts the steam flow rate byabout 50%. Patents pertaining to the fluid attrition mill addressed itsuse for producing boiler fuel; see the aforementioned patents to Tayloret al.

Fuel solids with 0.05 to 5.0 weight % or more water are attained by themeans discussed in the previous section—i.e., by evaporating the steamto that degree of hydration, or by cooling the superheated steam beforeevaporating it from the particles, or indirectly by completely dryingthe particles followed by a humidification step.

Secondary Substances

In some embodiments it is useful to introduce secondary substances tofuel solids before or during their comminution in the mill. Illustrativeexamples of secondary substances include grinding aids, catalysts,catalyst precursors, absorbents, and reducing agents, among othersubstances. Secondary substances include gases, such as natural gas,hydrogen gas, carbon monoxide, carbon dioxide, syngas, methane, steam,and other gases and gaseous mixtures. These can be added to the fuelsolids themselves, for instance while they are in a hopper or screwbefore entering the mill. Or the secondary substances can be introducedas dissolved compounds or as inclusions in the steam injections. Or thesubstances can be introduced to the mill by a port that is distinct fromand complements the steam nozzles and the fuel solids feed mechanism.The choice of introduction method will depend on the properties anddesired use of the secondary substance. For instance, it is convenientto add grits as grinding aids to the fuel solids before they enter themill. And it is convenient to provide water-soluble catalysts or theirprecursors or absorbents in the steam jets. Where the secondarysubstance is a gas, it is convenient to add it at practically any point:as a mixture with the steam, as a separately injected substance in thereaction chamber, or with the fuel solids before or during entry to themill. The choice of method of introduction of reducing agents willdepend upon the physical properties of the preferred agent(s). A commonreducing agent, tetralin, melts at −33° F. and boils at 403-406° F.,thus it may be injected as a gas in superheated steam, may be added as aliquid to fuel solids before their introduction to the reaction chamber,or may be added as a liquid to the chamber.

Grinding aids are particularly useful when the fuel solids include softor fibrous or molten materials. Many if not most types of biomass areexamples of soft or fibrous materials. Examples of grinding aids includesand, silica, alumina, metallic or carborundum grit, small coal solids,and the like. It is useful to have grinding aids present in an amount noless than 0.1% to 10% by weight of the soft or fibrous or moltenmaterial. It may be beneficial to employ a grinding aid that has asignificantly different density or solubility from the soft or fibrousor molten material so that the grinding aid can be recovered in asubsequent step, for instance in a separation from ash or from ascrubbed solution.

The benefit of adding a catalyst or its precursor to the mill is that itcan be made to cover exterior and interior surfaces of the groundparticles in a fine and thorough way. Thermal cycling is thought toprovide a differential pressure change effect that assists in “pumping”catalysts to the interior surfaces, though this will be more effectiveat smaller sizes and favorable flow shapes for catalytic particles. Theresulting fine distribution of catalyst provides improved kinetics andexpedites conversion when the comminuted fuel solids are subsequentlyraised to the critical temperatures and pressures required forcatalysis. In the present invention at least four types of catalysts areparticularly useful for inclusion during comminution in the mill:gasification catalysts, liquefaction catalysts, combustion catalysts,and cracking catalysts. By contrast, prior art users have sprayedcatalysts into scrubbers. In one embodiment the weight percent ofcatalyst added relative to the fuel solids is 0.05 to 50 wt. %, inanother embodiment it is 0.5 to 25 wt. %, in a further embodiment it is1 to 20 wt. %. In another embodiment it is 2.5 to 15 wt %, in stillanother embodiment it is 5 to 10 wt. %. Catalysts, catalyst precursorsand absorbents are found as minor components in fuel solids from severalnatural sources, notably including coal. Thus they may be present to amodest extent even if not added; the ranges above do not includecatalytic or catalytic precursor concentration ranges found in pristinenative fuel solids.

Gasification typically employs alkali or alkaline earth compounds ascatalysts; often these are carbonates; they reduce the conversiontemperature and speed up the conversion but they do not alter theproduct slate. An example of a gasification catalyst, which serves as acatalyst for gasification and which can also scavenge sulfur oxidecompounds during comminution, is calcium carbonate. Calcium carbonatedecomposes at about 1710° F., thus it is stable at the contemplatedgasification temperatures for the invention method but would decomposeat the temperatures in widespread use today. Potassium carbonate isanother example of a gasification catalyst useful in the presentinvention. Catalyst precursors can likewise be used instead of or inaddition to the catalysts. An example of a catalyst precursor forgasification is calcium oxide (CaO, also known as lime), which uponexposure to carbon dioxide reacts to form CaCO₃.

Acidic gasification catalysts can also be used. These include aluminaand silica, and can be used in conjunction with ceramic refractorymaterials in mills. Mineral acid such as hydrochloric can also be used,though refractory insulating materials may be less stable toward that.

Liquefaction catalysts by contrast are typically sulfides of transitionmetals; particularly useful catalysts are sulfides of tungsten,molybdenum, iron, cobalt, nickel, and combinations thereof in complexes.The liquefaction catalysts circumvent the need for a donor solventduring conversion; instead crude oil or residual refinery oils thatwould otherwise require coking can be used as a hydrogen donor. Anexample of a catalyst precursor for liquefaction is metallic iron, whichforms iron sulfide upon reaction with sulfur moieties in fuels.Additional exemplary catalyst precursors include soluble metal saltssuch as molybdenum ammoniate compounds and ferrous or ferric chloridecompounds; for instance these can be used to wet coal or another fuelsolid during or prior to comminution. Optionally after coating and orcomminution a small amount of hydrogen sulfide can convert thesecompositions to insoluble catalysts.

Optionally, combustion catalysts may be introduced to the solid fuelfeed, to the mill, or to a fuel composition in a process step subsequentto the mill. These catalysts serve one or more of three purposes:reducing nitrogen oxides to dinitrogen and dioxygen (2NO_(x)→xO₂+N₂);oxidizing carbon monoxide to carbon dioxide (2CO+O₂→2CO₂), and oxidizingunburned hydrocarbons to carbon dioxide and water(2C_(x)H_(y)+(2x+y/2)O₂→2xCO₂+yH₂O). The most active combustion catalystis platinum, however the cost and the potential for unwanted sidereactions make it non-optimal for some uses. Two other precious metalsthat can serve as combustion catalysts are palladium and rhodium.Platinum and rhodium are used as a reduction catalyst, while platinumand palladium are used as an oxidization catalyst. Cerium, iron,manganese and nickel are also combustion catalysts; because of nickel'sproclivity for dioxin formation, emissions from nickel-catalyzedcombustion may require specific containment measures. Catalystprecursors for any of these metals, if used, are not zero-valent metalsbut metal compounds that decompose to yield the zero-valent metal.Combustion catalysts tend to be poisoned by sulfur, and by metals suchas lead. When beneficiation is conducted in the mill for high-sulfurfuel solids such as Illinois coal, in one embodiment a combustioncatalyst is not added until a process step after comminution such as ina scrubbing step. The added catalyst may optionally be presented on asupport material such as silica or alumina, which may optionally befurther undergirded by a foundation of another material.

Another type of secondary substance is absorbents. Exemplary absorbentsinclude oxides of alkali metals or alkaline earth metals or ofmanganese. An example of an absorbent is CaO, which upon reaction withcarbon dioxide forms the compound CaCO₃. As noted above the carbonatedecomposes into CaO and CO₂ just above 1700° F.; the carbonate alsodecomposes in the presence of acid; thus carbon dioxide can besequestered by lime and then recovered. Examples of useful absorbentsare oxides of alkali metals and oxides of alkaline earth metals. Thus inmany cases absorbents are catalyst precursors for gasification. Anotherexemplary absorbent is carbon monoxide, which is useful in the inventionto react with and hence extract heteroatoms from the fuel. In oneembodiment the weight percent of absorbent used relative to the fuelsolids is 0.05 to 50 wt. %, in another embodiment it is 0.5 to 25 wt. %,in a further embodiment it is 1 to 20 wt. %. In another embodiment it is2.5 to 15 wt %, in still another embodiment it is 5 to 10 wt. %. Theranges above do not include sorbent concentration ranges found inpristine native fuel solids.

For added suspendability surfactants may be added to the fuel solids orthe mill as for the catalysts and other compositions noted above.Depending upon the surfactant these are typically useful in the range3-5 weight percent relative to the fuel solids, though in some cases aslittle as 50 ppm might be used. Ethoxylated hydrocarbons such as thosein a series provided by Rohm & Haas are among the more importantsurfactants in the United States for coal slurries. However the improvedfuel solids provided by the present method have intrinsicsurfactant-like properties, thus the inclusion of surfactant is optionaland may in fact merely increase the cost and hinder the efficiency ofcombustion or conversion.

Recovery of Solids

Following comminution the solids are conveniently recovered by one oftwo methods. The first method is evaporation as the leading edge of thesteam envelope is vented in a gaseous atmosphere such as air,dinitrogen, or carbon dioxide. Carbon dioxide is particularly usefulwhen the objective is to protect the solids from aerobic oxidation,because CO₂ is a byproduct of fuel use, and is heavier than air. Thesolids can be rehydrated by providing a light mist or humid gaseousenvironment such as moist air or another moist gas. The objective is toobtain fuel solids that contain about 0.5 to 5.0 or more weight percentof water relative to the fuel portion. In a particular embodiment theweight percent of water in the fuel is between 0.05 and 7.0.

Alternatively the solids can be recovered by scrubbing steam from theleading edge of the steam envelope such that it is blown into or througha liquid medium such as water, oil or an oil-and-water mixture. Theproportion of moisture and ash can vary widely in some fuels such ascoal and biomass, thus the moisture- and ash-free (MAF) content of thefuel solids provides a useful reference for describing its prevalence ina suspension; because ash is denser than carbonaceous material themoisture-free basis alone may be sufficient for designating the solidscontent of a suspension. Typically 35-40% solids (calculated as if fortheir moisture-free state) represents the maximum workable solidscontent for a suspension; beyond that level the suspensions becomethixotropic, and at 50% MAF solids they are often non-flowable.Suspensions having over 50% liquid medium by weight are particularlyuseful. In another embodiment the suspension comprises about 70% liquidmedium by weight. Note that a more polydisperse particle sizedistribution enables higher loadings in suspensions; such distributionscan be obtained for example from one mill run with a broad range ofparticle sizes, or by combining a plurality of less polydisperse runswhere each has a different mean. Particularly useful liquid mediainclude water, no. 6 fuel oil, recycle oil, and mixtures of one or bothof those oils with any ratio of water to oil by weight. The oils canserve as donor solvents for hydrogen transfer, but optionally anotherreducing agent such as tetralin may be added to the liquid media or thesuspensions to obtain; donor solvent(s) can represent 35% to 100% of theliquid phase.

Semi-Dehydration and Rehydration

The enthalpy proportional to the drying capacity of coal is relativelysmall. At 600 psi and 700° F., the enthalpy is 1450 BTU/lb. of steam. At20 psi and 250° F., the enthalpy of steam at the exhaust port is 1167BTU/lb, leaving a difference of 283 BTU per pound of steam available fordrying. Evaporating water requires 1100 BTU/lb., i.e., 3.89 pounds ofsteam are required to evaporate 1 pound of water. Thus for 1650 poundsof steam, 424 pounds of water can be evaporated. At a 1:1 ratio of steamto coal by weight, coal that initially had 10% moisture would becollected as essentially anhydrous coal. However it is desirable to havea hydration layer on the coal, thus evaporation of only 90% of the steamwould be more preferable. That can be attained either by misting withcool water at the outlet of the mill to wet the stream of collectedcoal, or by adjusting the steam input temperature and factoring in theinitial water content of the coal being fed into the mill. Adjustment ofthe mill's initial steam conditions is particularly convenient forobtaining a uniform and well-equilibrated hydration layer.

The ranges for efficient grinding and hydration in the mill tend to benarrow. Coal with an initial moisture content above about 12% does notemerge bone dry from the attrition mill when the shear field steam is at300° F. superheat and the coal is reduced to an upper diameter limit of40 microns. For instance Mississippi lignite containing 30% water byweight and using 700° F. steam was rapidly reduced to micron-size coal;the resulting product was still quite wet but was size-reduced. Also,coal may appear to be dry when it still has a relatively high watercontent, especially in younger coals, such as lignite and sub-bituminouscoals, that have a high proportion of functional groups containingoxygen atoms in their carbonaceous phases. Thus, for obtaining thedesired hydration layers by engineering design, it can also be importantto pre-dry coal that has a high water content. As necessary suchmoisture can be recaptured and reused to conserve water consumption bythe plant.

Fuel Type

Fuel solids provided by the apparatus and process above have distinctivecharacteristics, as is illustrated herein for coal. Unlike solidsobtained by traditional grinding, for comminuted coal obtained by theinvention method the organic structure's density is typically no greaterthan the density of the organic structure of the initial coal nuggets.Also, the porosity of the coal when water is essentially absent andvolatiles are factored out is not less than the porosity ofcorresponding structure in native coal, and tripling of the porosity hasbeen observed in lignite samples from the mill. Likewise, the surfacearea of comminuted coal is no less than for the surface area of thecorresponding structure in native coal nuggets, and because of theimproved porosity typically exceeds the exponential increase of surfacearea that one might expect from mere breaking of the particles intosmaller pieces. The speed and efficiency of coal combustion and chemicalconversion are dependent upon the porosity, the ratio of surface area tovolume, and the density of the coal, thus the improved physicalproperties have important benefits for leveraging the energy content ofcoal. Because the invention further provides for optional improveddistribution of secondary substances, including in the interior pores ofthe solids to the extent they are accessible, a new type of fuel isobtained which has advantageous properties for either combustion orchemical conversion.

In the art, removal of water is typically accomplished by holding a coalsample at a temperature slightly above its boiling point, and this isgenerally done in air. Although volatiles can be removed at 600-700° F.,for analytical purposes volatiles are typically removed by holding acoal sample at a temperature of about 1700° F. in the absence of air fora period of several minutes. To calculate pore volumes of the persistentcarbonaceous infrastructure of the coal, it is useful to merely factorout the approximate amount of volatiles based on weight percentages thatare typical for the coal and its mine source, and based on theapproximate density of the volatiles (often ca. 1 g/cm³). Porosity isoften measured by the surface area in m²/g determined by BET methodsusing a gas such as argon, nitrogen, helium or carbon dioxide.

The porosity and internal surface area of coal merit additionalcomments. Coal has a dendritic network of pores, not all originating atthe exterior surface. The pore sizes decrease over the length of thebranches, thus macropores (>50 nm) lead to mesopores (2-50 nm), which inturn lead to micropores (<2 nm). Micropores predominate in the morehighly ranked coals, whereas macropores predominate in low-ranked coalssuch as lignite. The degree of porosity falls but the robustness of thepore structure increases with the degree of coalification. Thusbituminous coals have 1.5 to 7% internal water in the native state; thiscan be removed and replaced again almost in its entirety because thepore structure is stable. Sub-bituminous coals have up to 10% internalwater in the native state, but only about half of that can be replacedafter the material has been dried. Lignite coals have up to about 30%internal water in the native state, and only about a third of that canbe replaced after the material has been dried. The reasons for ligniteand sub-bituminous behaviors after drying by conventional heating in airat 220° F. or more are not completely understood: they may be due toirreversible collapse of channels destroying a gel-like character of thenative undried state, and or they may be due to oxidative cross-linkingor the flow of hot oils and molten coal tars, sealing pores when thematerial is heated in air. Coals typically have in the range of 10-200m²/g of (internal) surface area; this surface area tends to be at itslowest in the highly ranked coals and at its highest in the low-rankedcoals such as lignite. Pore volume measurements are somewhat varied, andtypically reflect only the volume occupied by the water in native coalas opposed to the so-called volatiles. But for example, Silbernagelreported finding 0.134 mL of pore volume per gram of dry coal; thatrepresents about 12% of the coal by volume. See, Bernard G. Silbernagel,“Physical Characterization of Coal Surfaces,” Chap. 1, in InterfacialPhenomena in Coal Technology, G. D. Botsaris and Yuli M. Glazman, eds.,1989, pp. 1-32, at p. 17.

It seems quite likely that the level of porosity that is measurable isaffected by drying conditions for the coal. At elevated temperaturesinternal oils and or tars are likely to melt and flow, sealing orshrinking some access routes to pores. The mass percentage ofhigh-boiling volatiles in coal is high: up to 8% in anthracite, up to28% in bituminous coal, up to 45% in sub-bituminous coal, and up to 65%in lignite. Without being bound by theory, it is believed herein thateffects from oil and or tar flow that would otherwise occur areprevented or compensated in the invention method. This is explained inpart by steam explosion of sealed internal pores of fuel solids in themill, and in part by the fact that rapid reorientation of particles inthe mill favors no particular direction for tar flows, unlike slowergrinding with mechanical crushing. Oxidative cross-linking is alsominimized by the anaerobic conditions of the mill, thus minimizingshrinkage of pores in the carbonaceous infrastructure.

Due to the extensive fracturing and mixing in the mill, direct study isnot feasible for porosity changes that occur when the parent nuggets arecomminuted by the invention method. And due to expectation of steamexplosion effects, it is believed that significant changes in the shapeand size of specific pores occur during processing in the mill. Thus theretention of porosity is described indirectly herein using threemetrics. The first metric is the density of the fixed carbonaceousinfrastructure of the fuel when water and volatiles are factored out.The exact size and configuration of pores is irrelevant for densitybecause only the total relative volume of pores is reflected. The secondmetric is internal surface area per gram, the surface area that remainswhen the exterior surface area is factored out of the total surface areaof particles. External area obviously increases when fuel nuggets areground, thus only the internal surface area is relevant. Measurement ofsurface areas of fine internal cavities is complex and depends in parton the size, affinity and applied pressures of the probe molecules usedfor instance in BET measurements, thus the effect of artifacts inmeasurement should be considered when making these measurements. Thethird metric is the porosity of the coal. This can be determined by therelative amount of gas or fluid taken up by internal pores on avolumetric or gravimetric basis. The metrics may be gauged after removalof the volatiles and water contained therein, or by factoring out theknown content of volatiles and water in the material under study. Underthe method of the invention, materials are provided that preserve ormagnify the high porosity, the high surface area, and or the dearth ofdensity, each with respect to the fixed carbon infrastructure of thesolids.

Surprisingly, steam-coal suspensions obtained by the invention methodhave been burned essentially completely at a temperature well below2600° F., thereby avoiding formation of nitrogen oxides from thedinitrogen in air. Occasional “sparklers” have been observed in sometrials; these are believed to be due to aggregates of particles heldtogether by static charges where insufficient water was present inhydration layers, or held together by oxidative bonds formed when airwas not sufficiently excluded from the mill. Without being limited bytheory, it is believed that the ability to burn this coal so cleanly maybe due in part to the avoidance of refractory organic bond formation, incontrast to grinding and burning of ordinary coal. It is contemplatedthat the micronized particles of the invention will offer analogouseconomic and environmental advantages for gasification, liquefaction andcracking processes.

Fuel solids provided by the invention method also have surprisingstability in suspension in either hydrophilic media such as water,hydrophobic media such as no. 6 oil or recycle oil or donor solvent suchas tetralin, and water-and-oil mixtures. That is, the new fuel solidsremain suspended in such media for 7 days or more, even in the absenceof surfactants. This is particularly useful since it provides aninexpensive improvement for enriching the energy content of aqueousmedia such as black liquor by the addition of the new coalmicroparticles.

The distribution characteristics of catalysts or other secondarysubstances placed on surfaces of the fuel solids according the presentinvention are a function of how the substance is distributed. Forinstance, it is expected that catalysts that are added aswater-insoluble solids and for which temperatures in the mill are belowtheir melting point, associate with the fuel surfaces as fine particles,either physically embedded in the surface or more loosely associated. Inorder to obtain a finer distribution of such catalysts it is helpful toemploy them in an already finely ground form before their addition tothe mill. By contrast, catalysts that are added as solids and handled inthe melt state in the mill, or which otherwise undergo flow at theimpact energies present in the mill, are expected to “smear” on thesurfaces of the solids. Such smearing promises a more intimate and moreextensive association between the fuel surface and the catalyst.Catalysts such as molybdenum sulfide, which can smear by shedding layerssimilarly to friction-based exfoliation by graphite, provide analternate smearing mechanism during milling. Water-soluble catalysts areexpected to provide the most intimate association between the fuelsurface, since substantially all exposed surfaces are exposed to steam,the steam can dissolve such catalysts, and evaporation of steam tends toleave a fine residue of substances that have been dissolved in it.Solids layered with catalysts are also contemplated by permutations ofthese methods, for instance, providing to the mill a metallic catalystdissolved in an acid medium, whereby though the metallic catalyst is notwater soluble, it is nevertheless finely dispersed in the shear fieldand vortexes and on the fuel particles. Optionally a plurality ofcatalysts can be provided on the fuel surfaces.

The dispersion of catalytic solids is described here in terms of thesurface area of the fuel solid that is covered and or eclipsed by thecatalyst. The meanings of the terms “covered” and “eclipsed” areprovided in the definition section above. However, topographic featuresof the catalytic solids deposited on the fuel solids depend upondeposition conditions, and they can vary considerably, so the morphologymerits some further explanation. Consider very fine catalyst particlesthat are prolific but which have only a small portion of each particleembedded in fuel solid surfaces. In such a configuration the catalystmay account for over 50% of the total solid surface area, particularlyif the catalyst particle topography is rough, even though the catalyticinterface with the fuel solids may represent only 10% of the surfacearea of the fuel solids themselves. On the other hand, the actualworking surface of the catalyst is at the interface with the fuel solid,so the remainder of the catalytic surface is less available to the fuel,though the catalyst surfaces that are not in direct contact with thefuel may still carry on catalytic functions such as coordinating withhydrogen or with donor solvents. And yet a direct interface betweencatalyst and fuel solid is not completely necessary for catalyticefficiency. For instance, a graphene-like sheet of catalyst held awayfrom but in close proximity to a fuel solid surface at room temperatureis expected to be almost as efficient in catalysis at high temperatureas a directly interfacing catalyst surface.

The surfaces of internal pores in fuel solids of the invention areexpected to have surface deposits of water-soluble catalysts when suchcatalysts have been present in the mill, however it is difficult toanalyze the extent and depth of these internal deposits routinely orthoroughly. Thus external surfaces—i.e., the surfaces of the outermostfaces of a particle, not of its internal pores—are most convenientlyused for the description of the extent of dispersion of secondarysubstances on fuel solids. This is not a precise metric because thechoice is often arbitrary as to where an external surface ends and achannel, pore or other void space begins.

By means of the invention apparatus and method, fuel particles—and inparticular coal particles—covered and or eclipsed at their externalsurface by one or more secondary substances to any extent desired may beobtained. The thickness of the deposited secondary substance may also beengineered. In a particular embodiment the percentage of the fuelsolids' external surface area covered and or eclipsed by secondarysubstance(s) is at least 30%. In a further embodiment it is at least40%; in another embodiment it is at least 50%. In yet another embodimentit is at least 70%. In another embodiment it is at least 85%. In stillanother embodiment it is at least 95%. In a further embodiment it isapproximately 100%. The thickness of deposits of secondary substancesmay be quite fine, and under controlled conditions the deposition may beas thin as a molecular mono-layer. In a particularly useful embodiment,the layer is between 1 and 1000 nm thick, inclusive; in a furtherembodiment it is between 2 and 200 nm thick; in another embodiment it isbetween 3 and 30 nm thick; in yet another embodiment it is between 5 and20 nm thick; in still another embodiment it is between 10 and 15 nmthick.

As noted above the secondary substances provided on the fuel solids maybe catalysts, catalyst precursors, absorbents, or other substances. Inparticular, fuel solids containing surface-deposited catalysts based oniron, nickel, cobalt, platinum, palladium, rhodium, molybdenum,potassium, sodium, calcium, aluminum, silicon, magnesium, cerium, andmanganese or their oxides or carbonates are anticipated to beparticularly useful. Likewise fuel solids containing surface-depositedabsorbents based on oxides or carbonates of sodium, potassium, calcium,magnesium, and manganese are anticipated to be particularly useful.

In any case, the resulting product forms more stable suspensions in andhas improved compatibility in both coal-oil slurries and coal-waterslurries. In the prior art, surfactants were typically required tostabilize slurries of coal, that is, to maintain them as suspensions forextended periods, and were added either before or after a scrubbingstep. Surfactants commonly adsorb onto coal particles by theirhydrophobic end, leaving the hydrophilic end free. Many types ofsurfactants have been used for coal slurries; and in many cases had tobe present in 3-5% by weight in order to stabilize the suspensions,though in some cases as little as 50 ppm might be used. Ethoxylatedhydrocarbons such as those in a series provided by Rohm & Haas are amongthe more important surfactants in the United States for coal slurries.

Surfactants pose several problems. First, their materials costs issignificant relative to the commodity costs of coal. Also because of theheterogeneous diffusion of surfactants they require a thorough mixingstep, which imposes a process cost. Surfactants are also known to affectthe combustion, liquefaction and gasification properties of coalparticles. Surfactants are believed to hinder combustion by interferingsterically with the ability of atmospheric oxygen to reach the surfaceof the coal. Likewise, surfactants are thought to migrate to the mostchemically active sites on the coal surface, impeding catalyst accessand effectiveness for coal conversions.

Fuel Slurries and Suspensions

Suspensions made from fuel solid particles according to the presentinvention may be made as described above and have particular value. Thusaqueous suspensions may be burned in a diesel engine, and oil oroil-and-water suspensions may be burned in an oil burner. Alternativelythe suspensions may be gasified, for instance in a gasifier unit, or maybe liquefied for instance in a liquefier unit. Suspensions typicallyhave up to about 40% of fuel solids by weight as calculated on amoisture- and ash-free (MAF) basis. In one embodiment the suspensionshave between 20% and 40% of fuel solids by weight. In another embodimentthey have between 25% and 37% of fuel solids by weight. In a furtherembodiment they have between 30% and 35% of fuel solids by weight. About25% to 35% by weight of fuel solids is a particularly convenient rangefor suspensions, and in particular about 30% by weight of fuel solids isuseful, because such suspensions flow readily yet also have asubstantial percentage of their energy output provided by the solids.The percentage of fuel solids by weight in these embodiments iscalculated by including all the components of the particles in theweight of the fuel solids before suspension: these include thecarbonaceous infrastructure, secondary substances, particle watercontent, and particle volatiles content in the weight of the fuelsolids.

The purpose of a coal-oil mixture is, for example, to extend the supplyof #6 oil, residual fuel oil, or ship bunker fuel. The inventor wasamong the first in the industry to make barge loads of coal-oilmixtures. Typically coal represents 30-40% of the coal-oil mixture bymass. The energy in such a mixture is determined by the mass ratio ofcoal in the oil. Pure oil has about 18,000 BTU/pound×400 lb.oil/barrel=7,200,000 BTU's per barrel. The energy in coal alone is about35,000,000 BTU/ton.

Coal-water slurries are useful in that a diesel engine can be fueledwith them directly, with essentially identical performance to dieselfuel. The coal-water slurries leave ultrafine ash particles uponcombustion, however A.D. Little provided a method to remove them fromthe exhaust. A.D. Little also found that the slurries led to erosionproblems; the smaller and more uniform particles of the presentinvention provide a way to avoid this. Coal-water slurries are alsouseful for gasification processes, which otherwise uses particulatecoal. Stable surfactant-free mixtures are particularly valuable.

The slurries are also useful for handling fuels that have a “sticky”phase at high temperature when in the unsuspended solid form.Lower-ranked coals such as those from Wyoming, Montana, Alaska, andwestern Canada do not become sticky during heating, but bituminous coalsuch as Illinois #6 becomes very sticky. Slurries minimize the problemof handling these at high temperature.

The slurries also solve a transportation problem. The bituminous coalsare expensive to produce because they require either underground mines,which are costly to develop and also face extra safety issues, orbecause the less populated regions where surface mines are sociallyaccepted are not convenient to unscheduled rail or barge transportfacilities. The ability to create coal slurries that can be transportedoverland by pipeline or converted on site by liquefaction orgasification simplifies the logistics problem for handling material fromremote mines, particularly for a slurry that does not cause wear onpumps, valves or the like.

Improved Coal Body Surfaces

The hydration layer on individual particles is believed to beresponsible for the preventing mechanical fusion and discharging staticelectricity from the ultrafine particles. Also, the novel ambiphilicproperty was initially discovered after addition of sufficient water todrop the steam temperature noticeably for bituminous East Kentucky coalthat had been ground to a 40-micron maximum particle diameter by theinvention method; this cooling of the steam prevented dehydration fromreaching completion by evaporation upon venting of product from themill. As an example of calculating hydration layer thickness, considerre-addition of 5% water by weight to anhydrous coal, corresponding toabout 5×10⁻⁸ m³ added water per gram of anhydrous coal. For a bituminoussample having about 200 m²/g surface area (anhydrous, but with volatilespresent), if a 5 mass percent hydration layer is uniformly distributedacross the entire surface area this corresponds to a hydration layerabout 2.5×10⁻¹⁰ m thick on the coal surface, or about twice thatthickness if only half the surface is hydrophilic. That represents oneto two monolayers of water across the entire surface, depending upon howthe water molecules are oriented. However, hydration layers may besubstantially thicker. Also, hydrophobic volatiles exist at coalsurfaces, thus some surface zones may remain unhydrated due to phaseseparation phenomena. In addition, roughness on external surfaces leadsto some filling of external surface “valleys” with water, thus hydrationlayers will be thicker there. And although capillary action can occurwithin seconds or minutes to draw water into internal pores, thecomplete filling of pores with water or other solvents can require daysor even months at ambient pressure in part because gas displacement ishindered. Thus unless those pores retain water or, e.g., pump moistureduring thermal cycling, some internal surfaces remain unwetted on thetime scale for combustion or chemical conversion applications.

Where desired, more thorough wetting throughout coal particles can beaccomplished by using coal particles from which not all of the steam isevaporated. That is, the coal retains some condensed water followingmilling by the invention method. However, for purposes of exploitingambiphilic behavior in a suspension, the most important surface sitesare the external particle surfaces and the surfaces of the largest poresthat open at the external surfaces. Thus at least for ambiphiliccompatibility of the external surfaces, the choice is not critical as towhether water is re-added to anhydrous milled coal or whether water isretained from the milling step.

In one embodiment the invention provides external coal body surfacesthat have a hydration layer in the thickness range of 0.25 to 1000nanometers. In another embodiment the invention provides external coalbody surfaces that have a hydration layer in the thickness range of 1 to500 nanometers at their external surfaces. In a further embodiment theprovides external coal body surfaces that have a hydration layer in thethickness range of 3 to 300 nanometers at their external surfaces. Inyet another embodiment the provides external coal body surfaces thathave a hydration layer in the thickness range of 4 to 100 nanometers attheir external surfaces. In yet another embodiment the provides externalcoal body surfaces that have a hydration layer in the thickness range of5 to 50 nanometers at their external surfaces. In each of theseembodiments the hydration layers may optionally be present in zones thatare interspersed with zones of unhydrated external surfaces on the coal.

In another embodiment, the coal particles of the invention method may beprovided with from 0.25 to 10% of retained or re-added water. In anotherembodiment they may have 1 to 8% of retained or re-added water. In stillanother embodiment they may have from 3 to 6% of retained or re-addedwater. In a further embodiment the coal particles of the inventionmethod may be provided with about 5% of retained or re-added water.

Hydration layers can be surprisingly stable when they are juxtaposed toa carbonaceous surface. Although some fraction of that water may boiloff at the ordinary boiling point of water, monolayers of water canremain adsorbed on carbonaceous surfaces such as diamond up to ca. 570°F. (ca. 300° C.). This strong association at interfaces between waterand carbonaceous matter is believed to be responsible for thepersistence of the ambiphilic property observed in the invention method.Thus instead of shedding their hydration layers to undergo phaseseparation and precipitation of solids when coal particles are placed inaqueous suspensions, water at the coal surfaces appears to remainadsorbed to the coal, attracting solvation layers of hydrophilic liquidmedia even in the absence of surfactants. The failure of coal particlesfrom the prior art to remain stably suspended in water withoutsurfactants is tentatively attributed herein to extensive smearing ofhydrophobic volatiles across particle external surfaces duringmechanical crushing.

The persistence of water at particle surfaces normally would suggestthat those particles could not form stable suspensions in hydrophobicliquid media without the substantial use of surfactants. Howeverunexpectedly, coal particles made by the present invention do formstable suspensions in oils even without surfactants. Without being boundby theory, that result is rationalized here by analogy to the ambiphilicexternal surfaces of blood cells, which have a mosaic of hydrophilic andhydrophobic zones on the surface of the cell envelope. Under thishypothesis, for coal the comparable hydrophobic zones are patches oforganic volatiles at the external surface of the coal, whereas thehydration layers on the carbonaceous infrastructure populate thehydrophilic zones. It is thus the balance of the size and number of thezones that enables compatibility for suspension in either hydrophilic orhydrophobic media. The zones of volatiles, in turn, provide thehydrophobic or oleophilic surfaces needed for compatibility in oil. Itis possible that where hydration layers are only one or two monolayersin thickness, the oxygen atoms of the water molecules are uniformlyoriented outwardly in a polar media and that this also contributes tothe hydrophobic character of the coal body surface. But possibly thehydration layers have some other orientation of adsorbed water moleculesin a polar media.

In one embodiment invention provides coal body external surfaces havinga ratio of hydrophilic surface area to hydrophobic surface area in arange between about 25:75 and about 75:25. In another embodiment theratio is between about 35:65 and about 65:35; in another embodiment theratio is between about 45:55 and about 55:45.

Another surprising effect of hydration layers is their ability toprevent coal particles from aggregating. Coal particles made by theinvention method aggregate when they are anhydrous, but the aggregationceases immediately and essentially completely when hydration layers areprovided. This is opposite to what would be predicted by the law ofaffinity between like compositions. By that rule, a hydrated coalsurface would be expected to show a preference for associating with ahydrated zone on a neighboring particles, and for association betweenvolatiles at surfaces of neighboring particles. Thus it appears likelythat the effect of water in preventing aggregation is to dissipate ormuffle the effect of static electric charges on the coal.

The chemically most reactive sites for combustion and chemicalconversion have low activation energies for oxidation or catalyticreaction. At ordinary reaction temperatures, these sites are kineticallyaccessible for reaction only to the extent that they populate a surfaceof a particle. Unfortunately, for other reasons these moieties seem tobe the favored sites for forming an association between the solidsurface and surfactants, so surfactants kinetically hinder the approachof other molecules and reduce the efficiency of combustion or chemicalconversion. The invention reduces or eliminates the need for surfactantsin suspensions. Thus the invention provides ambiphilic hydrated coalbody surfaces that have a high population of available reactive siteswith a low activation energy for reaction in a pristine (i.e., free ofdioxygen, dinitrogen and the like) environment. In one embodiment thecoal body surfaces are in an aqueous suspension and the reaction iscombustion. In another embodiment the coal body surfaces are in an oilsuspension and the reaction is combustion. In yet another embodiment thecoal body surfaces are in an oil-and-water suspension and the reactionis combustion. In a different embodiment the coal body surfaces are inaqueous suspension and the reaction is a chemical conversion. In anotherembodiment the coal body surfaces are in an oil suspension and thereaction is a chemical conversion. In still another embodiment the coalbody surfaces are in an oil-and-water suspension and the reaction is achemical conversion. In some embodiments the chemical conversion ishydrogenation. In a further embodiment the ambiphilic coal body surfacesare in a hydrophobic liquid suspension, the reaction is hydrogenation,and the hydrophobic liquid comprises a hydrogen-donating organicsubstance.

In some embodiments of the invention the ambiphilic coal body surface ispopulated with a secondary substance. Particularly useful substances inthis respect include the catalysts, catalyst precursors, and absorbentsdisclosed above. Keeping in mind the relatively small amount of waterand the narrowness of the hydration layers, the secondary substances mayactually be dissolved in the hydration layer. Virtually any ratio ofwater to soluble secondary substance can be used in the hydration layer,but using 1% to 50% by weight of the secondary substance in thehydration layer is particularly useful. In another embodiment, theweight percent of secondary substance in the hydration layers is between5 and 25%; in yet another embodiment it is between 10% and 20%; inanother embodiment it is about 15%. Loading the internal pores of coalwith water, steam or hydrated secondary substances will be particularlyuseful in situations where rapid but uniform reactions are needed,whether in combustion, hydrogenation, liquefaction or gasification.

A secondary substance may also be present as a solid on the ambiphiliccoal body surface, either directly over a hydration layer, under ahydration layer, embedded in the coal surface, or associated with ahydrophobic zone on the ambiphilic surface. In a particular embodimentthe percentage of the ambiphilic coal body surface area covered and oreclipsed by secondary substance(s) is at least 30%. In a furtherembodiment it is at least 40%; in another embodiment it is at least 50%.In yet another embodiment it is at least 70%. In another embodiment itis at least 85%. In still another embodiment it is at least 95%. In afurther embodiment it is approximately 100%. At higher loadings theproperties of the secondary substance mask or swamp out the suspensionbenefits of the ambiphilic surface of the coal unless the secondarysubstance is soluble, defoliated or perhaps friable in the suspensionmedium. The thickness of deposits of secondary substances may be quitefine, and under controlled conditions the deposition may be as thin as amolecular mono-layer. In a particularly useful embodiment, the layer isbetween 1 and 1000 nm thick, inclusive; in a further embodiment it isbetween 2 and 200 nm thick; in another embodiment it is between 3 and 30nm thick; in yet another embodiment it is between 5 and 20 nm thick; instill another embodiment it is between 10 and 15 nm thick.

Combustion

The combustion temperature is a function of the strength of bonds thatmust broken when oxidizing the fuels—the stronger the bond, the higherthe temperature—and of the kinetic energy required for mass transfer ofcompounds to or from reaction sites. Solid fuels in particular canrequire higher temperatures because of the inefficiency of heat transferto the particle cores, and because of the kinetic hindrance for oxygento reach those bonds. The combustion of complex fuel solids such as coalnormally occurs at temperatures significantly above 2600° F. (1450° C.).At that temperature the N₂ gas which makes up about 70% of the earth'sambient atmosphere is oxidized along with the fuel solids, formingNO_(x) compounds that give smog its brown color. By contrast, steamsuspensions of the coal solids of the invention have been found to burnat apparent temperatures in the range of about 1800-2400° F. (about1000-1350° C.), thus they avoid the cross reaction of atmosphericnitrogen and oxygen.

Hydration layers on the surface of coal or resinous wood particles wouldboil off at even the lower combustion temperature. However the usefulproperties of the present invention can still be exploited in combustionby providing the fuel solids—with a hydration layer present—as adispersion, such as a suspension in a combustible liquid fuel.Alternatively the particles may be provided as a dispersion in water,steam or a low boiling solvent, whereby the particles are essentiallyspray-dried by injecting the dispersion in a spray pattern at highspeed, and then immediately burning the dehydrated injected spray or (ifinvolved) the gasified coal. The dispersion and spray-drying methodsminimize the presence of higher-burning aggregates, and the sprayedparticles may be burned directly while the just-dried particles arestill airborne. The smaller the particle, the faster and more uniformlyits interior may be heated. For sufficiently small particles of theinvention, the reaction can be nearly simultaneous with the applicationof heat, thereby avoiding overheating, tar formation, coking, andcharring of the particle surface found in longer-reacting processes.

The fuel particles thus provided may be loaded with combustion catalystssuch as those already described above, on solid support materials suchas silica or alumina as described above. The liquid dispersion media maybe flammable, such as number 6 oil, recycle oil, kerosene, gasoline,diesel fuel, or other flammable media. And or the liquid dispersionmedia may be highly volatile for spray-drying purposes, such as aqueous,methanol, ethanol, propanol (e.g, normal, iso or sec) or other lowalcohol. The combustion may be conducted in an oil burner, dieselburner, or gas flame. For instance, the gas flame could be a methaneflame, natural gas flame, white gas flame, or other flammable gas.

In one embodiment of the instant invention coal steam is ground tomicron or multi-micron fineness, resulting in diverse structures; thenthe micronized coal is made into a steam suspension, and this suspensionis burned at temperatures as low as 1800° F. (980° C.). In combustionexperiments for this work the exhaust was colorless and completelytransparent, like the burning of natural gas. The appearance of“sparklers” in the flame was observed only when the coal had beeninsufficiently ground or insufficiently dispersed. These sparklers areattributed to the presence of small clusters of fused or agglomeratedcoal powder which have a lower surface area per mass and cannot react asquickly during gasification, thus they require longer reaction times toreach a thermodynamic equilibrium and do not undergo completegasification in the flame before combustion. By comparison, normalmicronized coal burns at about a rate that one or two orders ofmagnitude lower than an obvious black body, requiring temperatures inthe range of 2600-2800° F., with a yellowish opaque flame andconsiderable amount of unburned carbon. Oil suspensions of the particlesof the invention can also be burned with improved properties, howeverthe to obtain the most efficient combustion and least coking of the oil,the liquid component of the suspensions should be a combination of oiland water.

Reaction kinetics of coal particles prepared by the invention methodhave been found to be as much as 2.8 times faster than those ofconventional coal particles of the same size, and it is believed thatthe surface area of the internal surface area of the invention coalparticles may be greater by one to three orders of magnitude than theexternal surface area. Also, by analogy to the combustion of natural gasthat it resembles, the combustion of the coal water suspensions and coalsteam are believed to proceed indirectly, first by a reaction betweencoal and steam to gasify the coal—i.e., forming syngas—followed byatmospheric oxidation of carbon monoxide to carbon dioxide and ofhydrogen to water.

Liquefaction

Direct liquefaction proceeds by liquefying coal directly through thepartial breakdown of the coal macromolecule under heat and pressure,with subsequent catalytic hydrogenation at higher pressure. Indirectliquefaction proceeds by gasification of coal, and catalyticpolymerization of the resulting gases such as by Fischer-Tropsch, Exxonmethanation, or the Mobil syngas to methanol process. Liquefaction iscurrently out of favor as a source of alternative fuels, however thepresent invention provides a more economically attractive approach tocoal liquefaction than prior technologies. Direct liquefaction ifthermodynamically more efficient and should result in lifecycleemissions of half as much carbon dioxide as is produced by indirectliquefaction.

Some key factors optimize the liquefaction of coal for the presentinvention. Excluding ambient oxygen gas during milling and thenceforthuntil liquefaction is completed avoids retrograde reactions in whichradicals from fragmented coal combine and form refractory bonds.Refractory materials formed in traditional milling cannot be liquefiedby conventional means apart from cracking, which is cost-intensive.Providing a source of carbon monoxide, low alkanes and or hydrogen gasin the mill in combination with liquefaction catalysts also facilitatesliquefaction in the mill and afterward, and can also exclude ambientoxygen gas. The carbon monoxide also extracts sulfur and oxygen atomsfrom the coal. Retaining the hydration layer on milled materials untilliquefaction is complete also facilitates the conversion.

The lower-rank sub-bituminous coals or lignites liquefy most readily butgive lower yields and lower ratios of liquids to gases than bituminouscoals, and normally produce fuels higher in oxygen. High rank bituminouscoals often require more severe conditions, and anthracite is generallyquite difficult to hydrogenate to a liquid. In part the ease ofliquefaction is correlated to the carbon:hydrogen atomic ratio of thestarting material: the more hydrogen, the better. Bituminous fuel isuseful for several reasons. Its atomic ratio of H:C is roughly 0.7:1.0.Liquefaction of coal requires attaining a 1:1 atomic ratio of H:C (1:12on a weight basis). Lignite and sub-bituminous coal sources areabundant, and these coal sub-types are also very reactive, though it isbetter to remove some or all of their water before liquefaction orgasification. Coals containing the minimum H:C ratio produce manyinsoluble and refractory substances upon heating, which renders themless efficient as combustion fuels. A more preferred ratio is an H:Catomic ratio of 1.2:1. This is relatively high versus the results ofothers. An H:C atomic ratio of 1.5:1 is probably the maximum practicalachievable level.

In one embodiment liquefaction is achieved very rapidly (i.e., in 10 to15 seconds) by heating the coal particles rapidly in a hydrogen gasatmosphere with a liquefaction catalyst. By contrast, the contact timefor mixtures of coal and vehicle oil normally require from about 20minutes to 1 hour at pressure and temperature for as much as 3-4 barrelsof liquids per ton of coal in most hydrogen-donor solvent schemes.

Although there may be a soak time at a somewhat elevated temperatureduring dissolution, the rate of heating to liquefaction temperatureshould be as rapid as possible to prevent repolymerization of reactivefragments formed from the rupture of the weakest bonds in the coal attemperatures lower than those for which hydrogen transfer becomes rapid.Temperatures to produce liquids typically range from 750 to 1020° F.(400 to 550° C.). The lower threshold for liquefaction is about 570° F.(300° C.), which corresponds to the upper threshold at which hydrogenand or adsorbed hydration layers boil off the surface of carbonaceousmaterials. The properties of the comminuted particles of the inventionare believed to enable faster liquefaction and gasification, though notnecessarily lower-temperature or lower-pressure conditions forliquefaction or gasification.

It is believed here that bulk coal suffers from low (surface)area-to-volume ratios, thus its heat transfer from the surface to thecenter of a coal particle is inefficient because a thermal gradientexists in which the lowest temperature is at the particle core. Also,coal which is heated at too high a temperature even in the absence ofoxygen is believed here to produce internal radicals that react to forma highly cross-linked network of refractory bonds known as a char; charsare characteristic of coke, for instance. Chars burn with lessefficiency than ordinary coal; that is rationalized here as being due tothe difficulty of breaking cross-links thermally, and the loss of easilyoxidizable groups on the surface; the same characteristics will make itunsusceptible to other chemical conversions apart from a crackingprocess. By contrast, non-char coal materials that lack a highlycross-linked network can be converted to other desirable fuel typesreadily by a liquefaction or gasification process. Thus it is preferableto use fuels with small particles, because their interior is heatedrelatively quickly and uniformly relative to the remaining mass of theparticle; the combination of a small particle size and a liquid mediumaround the particle provides a minimum of byproducts from overheatingthe surface.

The pressures required for liquids production by hydrogenation rangefrom about 500 to 4,000 psi. The rank of coal, liquefaction scheme,desired end product, mineral matter and added catalyst present, andextent of conversion determine the optimum pressure. Lower rank coalscan be liquefied at lower pressures. These pressures can be accommodatedfor liquefaction within the mill itself. Note that the design andoperating costs for mills are lower when the plant specifications callfor liquefaction to be performed subsequent to and not during milling.Metals can catalyze coal liquefaction and are especially effective inthe temperature range in which liquids are formed. It is helpful thoughnot absolutely necessary to conduct the liquefaction in the presence ofthe metal-containing ash. It is helpful to have some water present; inthe range of 4% to 10% by weight relative to the fuel is a convenientrange. Complete drying has been demonstrated to be deleterious.

The chemistry of liquefaction reactions in the invention, i.e., in themill and beyond, can be summarized as follows.

Steam reformation of coal or natural gas→

H₂ (desired product)+CO₂ (collectible, sequester-able product)+CO

CO+heteroatoms→heteroatom oxides (collectible, removes poisons ofcatalysts)

Solid fuels+H₂→liquid fuels

One advantage of the ability to reform coal directly to obtain theneeded syngas is that the method does not rely on the availability ofnatural gas. Contrast this with Canadian coal tars, which are found incombination with abundant natural gas but whose processing byconventional liquefaction will require consumption of all the naturalgas present in those tars.

If hydrogenation proceeds too far, it typically results in C₁-C₄ gasbyproducts, which is an unnecessarily costly way to make natural gas.Typical byproducts also include carbon dioxide, water, and ammonia. Thewater, ammonia and low alkane byproducts from conventional liquefactionrepresent an enormous waste stream because the hydrogen gas used to makethem is “wasted,” since these products can be had more inexpensively byother routes, and much more carbon dioxide is produced than in DCL.

The efficiency of hydrogen use for liquefaction is as follows. For ICLor indirect liquefaction via syngas and catalytic conversion, typicallya ton of coal yields about 2 barrels or less of crude oil, thoughproducers aim for an efficiency of 2.5 barrels per ton. The maximumtheoretical yield is 3.5 barrels per ton; the attainable yield by theinvention method is anticipated to be in the range of 3 barrels per tonof coal for a grade such as sub-bituminous or Wyodak coal. In any case,the common practice for liquefaction arts is to inject hydrogen gas intothe coal-oil mixture; this slurry maximizes the amount of product perton of coal. The reaction proceeds as outlined below.

Coal−(steam+grind)→processor−(inject steam+¼″ coal)→ultrafine coal

Scrub ultrafines with “recycle” oil of any type, e.g., refinery bottoms

Recycle oil extracts particulates from steam with the mist→add tocoal-oil mixture

Coal-oil mix→storage (inventory). The invention provides an improvedcoal-oil slurry.

Inventory→(a) liquefaction, (b) hydrogenation, (c) clean-up, and (d)re-work.

Conversion efficiencies for transforming solid to liquid can be on theorder of 95%; efficiency for converting oils is on the order of 60-65%,where efficiency is calculated on an MAF basis in the absence ofnitrogen, oxygen and sulfur moieties in the beginning fuel.

Heteroatom removal can be accomplished during liquefaction or in a priorstep in the present invention by the following means; this removespoisons to catalysts for later processing. The variability of impuritiesfrom different natural sources has a limited effect on efficiency ofoperation, because liquefaction plants are typically tuned to coalproduced by particular mines in order to obtain consistent results withthe content of water, ash, sulfur, and heat output. Thus whether theplant burns, liquefies, gasifies, or some combination thereof, thevariance in the stoichiometry will be minor.

S→SO₂ (optionally by O₂)

Natural gas (CH₄)+steam (H₂O)→CO+3H₂

CO+O in the coal→CO₂

CO+S and N in the coal→>CO compounds

CO₂+S and N in the coal→SO₂+NO_(x)+CO

Gasification

The DOE has attempted to identify the best technologies for coalgasification and combustion, for instance Nexgen and the IGCCtechnologies, as well as conversion to liquid fuels and valuablebyproducts. However the industry has not widely adopted these, becausetheir reliability and energy efficiency is too low, partly because ofthe extreme operating conditions and substantial losses of heat theycannot recoup from gasifiers. Nevertheless improved processes to obtainfuel gases must be found. Recently natural gas was available for $8 permillion BTU, but is expected to rise to $14-$15 per million BTU assupply fails to match demand. In many ways natural gas is also morevaluable as a chemical feedstock than as a fuel, and the demand forfeedstocks will also tend to drive up the price. Bituminous coal andlignite are useful for gasification for the same reasons as forliquefaction.

An exemplary common temperature range for gasification is about1200-1600° F. (650-870° C.), though the temperature is lower whencatalysts are present. By contrast many commercial gasifiers mustoperate at 2300-2400° F. (1260-1320° C.) and may even be in the range of2600-2800° F. Consequently their ash is converted to molten slag that isnot merely worthless but costly to dispose of. At high temperatures andpressures CO₂ and CH₄ also represent a substantial portion of the gasproduced in most gasifiers, and conventional gasification units alsorequire the presence of a small, controlled amount of oxygen in order toinitiate a domino reaction by exothermic combustion. By contrast toconventional methods, the current invention appears to produce little orno CO₂ or CH₄ during gasification; this conclusion is based in part onGibbs free energy minimization simulations for input slates using ASPEN™software, now known as ASPENPLUS™, from the AspenTech, Aspen Technology,Inc., 200 Wheeler Road, Burlington, Mass. 01803 USA. Gasification by theinvention method also requires no oxygen to be present, by contrast toprior art, moreover the conditions of the invention method produce dryfriable ash that has significant marketable value as a material in itsown right. The chemistry of gasification reactions for the invention canbe summarized as follows.

Coal+H₂O→CO+H₂ and or Natural gas+H₂O→CO+H₂ (steam reformation)

CO+coal heteroatoms→heteroatom oxides

H₂→2H (homolytic cleavage)

and or H₂→H⁺+H⁻ (heterolytic cleavage).

Byproducts can be removed, for instance using absorbents for H₂S in thegasifier and absorbents for SO_(x) in combustion. The absorbents sublimeat low temperatures; the MgS and CaS form is desirable because it can becaught in bag. IGCC provides byproducts in the form of slag. Finelydivided, clean ash is very salable as cement, for instance at $25/ton or$22.50 per ton of coal, and avoids the cost of remediation. SiO_(x) andAlO_(x) form slag along with alkali and alkaline earth compounds, whichsoften at boiler temperatures.

Ordinarily refractory materials are difficult to gasify, however it iscontemplated here that at sufficient extents of comminution and in thepresence of water, suspensions of refractory materials comminuted to asufficiently small size by the invention method may undergo smoothin-flame gasification as discussed above for combustion by the inventionmethod.

In-Line Configurations

The processor may be used to advantage in various in-lineconfigurations. Referring now to FIG. 4, an exemplary embodiment isdescribed here for illustrative purposes. A steam source (1) is providedwhich supplies steam for the shear field and vortexes in the processor(4). Optionally steam source (1) may also provide steam for drying andde-aerating the coal source (2) prior to its introduction to theprocessor (4). Here the coal has already been crushed to ¼″×0″ nuggets.The steam from source (1) and the coal from source (2) may alsooptionally be supplemented with a secondary substance (3) before theirintroduction to the processor (4). An optional absorbent (5) or optionalcatalyst or catalyst precursor (6) may be provided to either the coalsource (2) or directly to the processor (4).

The steam products (7) contain the classified, comminuted fuel particlesand are vented from the processor (4); in one embodiment the steamproducts (7) are provided in combination with gas from a clean-up unit(9) for clean boiler fuels (10) in conventional power generation. Inanother embodiment the steam products may be routed directly to agasifier (8) followed by clean-up in unit (9). In a third embodiment thesteam products (7) are routed to an oil-, water-, oroil-and-water-scrubber (16) such as a Venturi scrubber, and from thereto a slurry unit (17) in which catalyst may optionally be added tocomplement or substitute for the catalyst coating in the processor (4).The slurries are sent in one embodiment to a liquefaction unit (18).Products of such liquefaction units are typically useful for syntheticcrude oil, jet fuel and gasoline. Alternatively the slurries can berouted to a gasifier unit (19), and from thence to the gas clean-up unit(9).

Gas from the clean-up unit (9) may then be processed in a synthesismanifold or for a single dedicated synthesis use, as follows. In oneembodiment the gas is sent to a hydrogen separation unit (11); suchunits are useful for fuels for turbines, boilers, steam and electricityproduction. In a different embodiment gas from unit (9) is routed to aunit (12) for syngas production for refinery processes; such units areuseful for production of hydrogen, fertilizers, ammonia, etc. In yetanother embodiment the output of unit (9) is used in a methanolsynthesis unit (13) to provide industrial chemical feedstocks and liquidtransport fuels. In still another embodiment, the product of unit (9) isdirected to a dimethylether (DME) synthesis unit (14); DME synthesisprovides clean high-energy liquids for transport fuel. In a fifthembodiment, the output of unit (9) is employed in Fischer/Tropschsynthesis to obtain clean diesel.

EXAMPLE 1 Calculations for Using a 650° F., 200 psi Steam Source

Assumptions and figures are shown for exemplary calculations at aninitial temperature of 650° F. and 200 psi in the boiler acting as asteam source for a grinder constructed according to the invention. FIG.1 graphically depicts the result for calculating dryness of theresulting coal that is obtainable based on only the input levels ofsteam based on these assumptions.

Assumptions:

Steam Conditions: 650° F., 200 PSI before nozzles Inlet Temp Coal 60° F.Coal/Steam Ratio 0.75 lb steam/lb coal Enthalpy before nozzles 1,350BTU/lb steam @ 650/200 psi inlet Enthalpy after nozzles available 1,160inside grnider to heat coal and moisture Enthalpy Available 190 BTU/lbsteam available or enthalpy per lb of coal 143 BTU enthapy per poundcoal incl moisture Exhaust Temperature: 250° F. delta T 190° F. SpecificHeat Coal 0.201 BTU/lb heated to boiling point @250° F. Specific HeatWater 1 BTU/lb heated to boiling point @250° F. Evap # water at boiling961.7 BTU/lb Coal is 100% wt less water

EXAMPLE 2 Calculations for Using a 700° F., 200 psi Steam Source

Assumptions and figures are shown for exemplary calculations at aninitial temperature of 700° F. and 200 psi in the boiler acting as asteam source for a grinder constructed according to the invention. FIG.2 graphically depicts the result for calculating dryness of theresulting coal that is obtainable based on only the input levels ofsteam based on these assumptions.

Assumptions:

Steam Conditions: 700° F., 200 PSI before nozzles Inlet Temp Coal 60° F.Coal/Steam Ratio 0.75 lb steam/lb coal Enthalpy before nozzles 1,375BTU/lb steam @ 700/200 psi inlet Enthalpy after nozzles available to1,160 inside grnider heat coal and moisture Enthalpy Available 215BTU/lb steam available or enthalpy per lb of coal 161 BTU enthapy perpound coal incl moisture Exhaust Temperature: 250° F. delta T 190° F.Specific Heat Coal 0.201 BTU/lb heated to boiling point @250° F.Specific Heat Water 1 BTU/lb heated to boiling point @250° F. Evap #water at boiling 961.7 BTU/lb Coal is 100% wt less water

EXAMPLE 3 Calculations for Using a 750° F., 200 psi Steam Source

Assumptions and figures are shown for exemplary calculations at aninitial temperature of 750° F. and 200 psi in the boiler acting as asteam source for a grinder constructed according to the invention. FIG.3 graphically depicts the result for calculating dryness of theresulting coal that is obtainable based on only the input levels ofsteam based on these assumptions.

Assumptions:

Steam Conditions: 750° F., 200 PSI before nozzles Inlet Temp Coal 60° F.Coal/Steam Ratio 0.75 lb steam/lb coal Enthalpy before nozzles 1,400BTU/lb steam @ 750/200 psi inlet Enthalpy after nozzles 1,160 insidegrnider available to heat coal and moisture Enthalpy Available 240BTU/lb steam available or enthalpy per lb of coal 180 BTU enthapy perpound coal incl moisture Exhaust Temperature: 250° F. delta T 190° F.Specific Heat Coal 0.201 BTU/lb heated to boiling point @250° F.Specific Heat Water 1 BTU/lb heated to boiling point @250° F. Evap #water at boiling 961.7 BTU/lb Coal is 100% wt less water

EXAMPLE 4 Liquefaction

This example illustrates one embodiment of co-processing coal andhydrogenation catalyst during comminution, and also illustrates thestep-wise heating sequence to maximize the yield of desired products.

20 tons (2,000 pounds per ton) per hour of run-of-the-minesub-bituminous coal is put through a hammer mill whose grate is set todeliver ¼″×0″ product to a surge hopper. This sized coal is dischargedby gravity to a screw feeder which is fitted with a steam jacket whosefunction is to evaporate some of the coal moisture and displaceentrained air from the coal feed to the processor. A small portion ofthis steam is condensed and the condensate is returned to the boiler forre-boiling. A separate feeder delivers fresh make-up catalysts from asource thereof to the first flites of the main screw feeder to beadmixed with the coal during transit to the processor. This catalystfeed contains a principal hydrogenating catalyst which is a sulfide of ametal selected from the group consisting of molybdenum, nickel, cobalt.Iron, alkali metal, compounds of alkaline earth metals, and combinationsthereof, may also be provided as a shift reaction catalyst.

A boiler provides superheated steam to the processor at a sourcetemperature of about 750° F. (400° C.) and source pressure of about 200psi, where the steam is provided to the processor at a rate of 30,000pounds per hour. The enthalpy of this steam is 1400 BTU per pound or42,000,000 BTU per hour. For purposes of calculation, a typical coal isexemplified here by the following composition:

Component Mass % of Total Lbs./Ton Ash 12 240 Water 20 400 Sulfur 2 40Oxygen 4 80 Other 4 80 Carbon 58 1160

The discharge temperature of steam from the processor is about 250° F.(ca. 120° C.), at which temperature the enthalpy of the processing steamis 1165 BTU/lb or 35,000,000 BTU per hour, a drop of 7,000,000 BTU perhour spent on evaporating coal moisture and heating the coal to exhausttemperature. Using a specific heat for coal of 0.201 BTU/lb/° F. and a190° F. (ca. 88° C.) temperature swing, a total of 1,500,000 BTU arespent heating the coal leaving 5,500,000 BTU to evaporate moisture fromthe coal to an enthalpy of 1100 BTU/lb sufficient to evaporate 5,000lbs. of water per hour. Therefore it is estimated the moisture contentof the processed coal drops by 125 lbs./ton of coal to 275 lbs. waterper ton or a final moisture content of 13.75%.

The coal/steam discharge from the processor reports to a scrubberwherein recycle heavy residue (derived from process) is sprayed todeliver a catalyst-containing coal in donor oil suspension to heatedprocess intermediate storage. This suspension is about 35% coal andabout 65% oil and un-reacted solids from prior runs.

Discharging processor output into a scrubber and de-mister allows theuser to recover an extremely uniform dispersion of coal-supportedhydration catalyst on the coal particles. It is contemplated that in theabsence of oxygen and nitrogen the sulfur moiety of the catalyst adsorbsto the carbon of the coal. The mixture of hot coal and preheatedprocess-derived recycle oil are maintained at a temperature of about121° C. (250° F.). At this temperature the dispersion is charged with500 psi to about 2000 psi of output of carbon monoxide and hydrogen,e.g., from a gasifier. This step is done at such a low temperature toensure that during initial heating the donor solvent recycle oil ismaximally hydrogenated by the catalyst; it is believed that this occursby transfer of monatomic hydrogen but the invention is not limited bythe theory.

A preprogrammed heating step is then imposed to a temperature of between300 and 350° C. (572-662° F.). This step is performed to allow thecarbon monoxide and water to extract many heteroatoms from the coalstructure and convert the otherwise free radicals to phenolics and thelike, depolymerizing the coal and avoiding creation of refractorysubstances.

Thereafter the gaseous overpressure is augmented by relatively purehydrogen from the gasifier, and the temperature is increased to betweenabout 400 and 450° C. (752-842° F.). It is believed that as thetemperature increases the contribution of the hydrogenated donor solventwanes and the coal hydrogenation primarily occurs by catalyzed monatomichydrogen addition.

In a more particular embodiment, a working suspension is withdrawn fromintermediate storage at a rate of about 4.3 gallons per second, and amixture of carbon monoxide and hydrogen is admixed up to a pressure ofbetween 500 psi and 2000 psi whereupon a programmed heating cycle isinitiated to achieve an intermediate holding temperature of about 325°C. (617° F.) and thereafter to a final temperature of about 475° C.(887° F.). This heating may conveniently be achieved through electricimmersion heaters in a series of treatment zones, and turbulators may beinserted into the transport tubing to promote more complete mixing ofvarious reactants. Following liquefaction, standard procedures arefollowed to recover product, donor solvents and reprocessing feedstocks,gasification and coking materials and the like.

The typical anticipated yield for total conversion under theseconditions is in excess of 90% for carbonaceous material in the coal andin excess of 60% for the oil portion.

EXAMPLE 5 Gasification

Coal is prepared and introduced into the processor as in theliquefaction example above. The coal feed can optionally be admixed withpetroleum coke and or other carbonaceous substances to an extent ofabout 60% by weight. The steam requirements for complete carbonoxidation at a carbon:water molar ratio of 1:1 will be 1755 pounds ofsteam per ton of sub-bituminous coal which is 58% carbon on a moisture-and ash-free (maf) basis. If, however, a greater amount of hydrogen isneeded or if it is desired to reduce carbon monoxide greater amounts ofsteam (water) are preferred. Gasification in this example is conductedat atmospheric pressure; ambient pressure gasifiers are relatively easyto configure from light weight sheet metal and light weight tubing.

Gasification can be conducted in parallel with liquefaction of the samecoal source. Thus, for this example a substantial carbon monoxide gascontent is provided to satisfy the liquefaction needs, and thereafter asecond feed from the gasifier contains a minimum of carbon monoxide anda maximum of hydrogen. For some arrangements it is more economical totake a portion of the output of the main liquefaction processor toprovide the gasifier feed.

The coal/steam output of the processor is heated allo-thermally to atemperature of between 1200° F. (650° C.) and 1600° F. (870° C.),preferably at a temperature of about 1400° F. (760° F.), whereupon thecarbon is oxidized essentially immediately. During cool-down the gasundergoes an ash removal step in a hot cyclone, an aqueous spraycontaining sulfur compound absorbents prior to extracting thehydrogen/carbon monoxide needs of the liquefaction unit. Thereafter ashift catalyst is introduced to the remaining gas to maximize theoxidation of carbon monoxide with the concurrent production of morehydrogen.

Variations

Although specific embodiments of the present invention have beendescribed above in detail, the description is merely for purposes ofillustration. In addition to the embodiments above various modificationsof, and equivalent elements and steps corresponding to, the disclosedaspects of the exemplary embodiments, can be made by those skilled inthe art without departing from the spirit and scope of the presentinvention defined in the following claims, the scope of which is to beaccorded the broadest interpretation so as to encompass suchmodifications and equivalent structures.

1) An ambiphilic coal body surface, comprising a coal surface inassociation with and juxtaposed to a hydration layer. 2) An ambiphiliccoal body surface according to claim 1, wherein the hydration layer hasa thickness in the range of 0.3 to 3 nanometers. 3) The ambiphilic coalbody surface of claim 1, wherein the surface possesses a high populationof available reactive sites that have a low activation energy forcombustion and chemical conversion. 4) The ambiphilic coal body surfaceof claim 1, wherein two such coal surfaces each having a hydration layerexhibit a lower tendency to aggregate with each other, than do twosubstantially anhydrous surfaces of the same type of coal body tend toaggregate in the absence of the hydration layers. 5) The ambiphilic coalbody surface of claim 1, wherein the surface is compatible with ahydrophilic liquid. 6) The ambiphilic coal body surface of claim 1,wherein the hydration layer is further in association with andjuxtaposed to a hydrophilic liquid. 7) The ambiphilic coal body surfaceof claim 6, wherein the hydrophilic liquid further comprises an additiveto enhance combustion. 8) The ambiphilic coal body surface of claim 1,wherein the surface is compatible with a hydrophobic liquid. 9) Theambiphilic coal body surface of claim 1, wherein the coal surface isfurther comprised of volatiles that lack a hydration layer, and whereinthe volatiles are in association with and juxtaposed to a hydrophobicliquid. 10) The ambiphilic coal body surface of claim 9, wherein thehydrophobic liquid comprises a hydrogen-donating organic substance. 11)The ambiphilic coal body surface of claim 1, wherein the surface isessentially free of surfactant. 12) The ambiphilic coal body surface ofclaim 11, wherein the surface possesses a high population of availablereactive sites that have a low activation energy for combustion andchemical conversion 13) The ambiphilic coal body surface of claim 1,wherein the hydration layer is adsorbed to the coal surface. 14) Theambiphilic coal body surface according to claim 1, wherein at least amolecular monolayer of water adheres to a substantial portion of thecoal surface up to a temperature of about 570° F. at ambient pressure.15) The ambiphilic coal body surface of claim 1, further comprising acatalyst or catalyst precursor dissolved within the hydration layer. 16)The ambiphilic coal body surface of claim 1, further comprising acatalyst or catalyst precursor disposed as a solid on the oppositesurface of the hydration layer or between the hydration layer and thecoal surface. 17) The ambiphilic coal body surface of claim 16, whereinthe catalyst or catalyst precursor is dispersed over at least 40% of thesurface, and the surface is selected from the group consisting of anexterior surface and an interior surface of a coal particle. 18) Theambiphilic coal body surface of claim 1, further comprising an absorbentdissolved within the hydration layer. 19) The ambiphilic coal bodysurface of claim 1, further comprising an absorbent present as a soliddispersed at an outer surface of the hydration layer or between thehydration layer and a coal surface. 20) The ambiphilic coal body surfaceof claim 19, wherein the absorbent is dispersed over at least 40% of thesurface, and the surface is selected from the group consisting of anexterior surface and an interior surface of a coal particle.